diff --git a/src/actor.h b/src/actor.h
index 6e64b6033e..e7d84f09d5 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -1025,6 +1025,10 @@ public:
 	double			projectilepassheight;	// height for clipping projectile movement against this actor
 	double			CameraHeight;	// Height of camera when used as such
 
+	double			RadiusDamageFactor;		// Radius damage factor
+	double			SelfDamageFactor;
+	double			StealthAlpha;	// Minmum alpha for MF_STEALTH.
+
 	SDWORD			tics;				// state tic counter
 	FState			*state;
 	//VMFunction		*Damage;			// For missiles and monster railgun
diff --git a/src/info.cpp b/src/info.cpp
index 6f9b95f36d..b8abba9760 100644
--- a/src/info.cpp
+++ b/src/info.cpp
@@ -255,10 +255,6 @@ PClassActor::PClassActor()
 	BurnHeight = -1;
 	GibHealth = INT_MIN;
 	WoundHealth = 6;
-	FastSpeed = -1.;
-	RDFactor = 1.;
-	SelfDamageFactor = 1.;
-	StealthAlpha = 0.;
 
 	DropItems = NULL;
 	// Record this in the master list.
@@ -311,10 +307,6 @@ void PClassActor::DeriveData(PClass *newclass)
 	newa->BloodColor = BloodColor;
 	newa->GibHealth = GibHealth;
 	newa->WoundHealth = WoundHealth;
-	newa->FastSpeed = FastSpeed;
-	newa->RDFactor = RDFactor;
-	newa->SelfDamageFactor = SelfDamageFactor;
-	newa->StealthAlpha = StealthAlpha;
 	newa->HowlSound = HowlSound;
 	newa->distancecheck = distancecheck;
 
diff --git a/src/info.h b/src/info.h
index fd89145465..f2a6101e9b 100644
--- a/src/info.h
+++ b/src/info.h
@@ -297,10 +297,6 @@ public:
 	PalEntry BloodColor;	// Colorized blood
 	int GibHealth;			// Negative health below which this monster dies an extreme death
 	int WoundHealth;		// Health needed to enter wound state
-	double FastSpeed;		// speed in fast mode
-	double RDFactor;		// Radius damage factor
-	double SelfDamageFactor;
-	double StealthAlpha;	// Minmum alpha for MF_STEALTH.
 	FSoundID HowlSound;		// Sound being played when electrocuted or poisoned
 
 	FDropItem *DropItems;
diff --git a/src/namedef.h b/src/namedef.h
index 196c41fd05..7c63eb7859 100644
--- a/src/namedef.h
+++ b/src/namedef.h
@@ -392,6 +392,7 @@ xx(Radius)
 xx(ReactionTime)
 xx(MeleeRange)
 xx(Speed)
+xx(FastSpeed)
 xx(Clamp)
 xx(VisibleStartAngle)
 xx(VisibleStartPitch)
diff --git a/src/p_interaction.cpp b/src/p_interaction.cpp
index 4c23c8123c..2af2a3da13 100644
--- a/src/p_interaction.cpp
+++ b/src/p_interaction.cpp
@@ -1022,7 +1022,7 @@ static int DamageMobj (AActor *target, AActor *inflictor, AActor *source, int da
 	}
 	if (target == source && damage < TELEFRAG_DAMAGE)
 	{
-		damage = int(damage * target->GetClass()->SelfDamageFactor);
+		damage = int(damage * target->SelfDamageFactor);
 	}
 
 	// [MC] Changed it to check rawdamage here for consistency, even though that doesn't actually do anything
diff --git a/src/p_map.cpp b/src/p_map.cpp
index 70b18df7fa..7e110dcbf4 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -5680,7 +5680,7 @@ int P_RadiusAttack(AActor *bombspot, AActor *bombsource, int bombdamage, int bom
 			{
 				points = points * splashfactor;
 			}
-			points *= thing->GetClass()->RDFactor;
+			points *= thing->RadiusDamageFactor;
 
 			double check = int(points) * bombdamage;
 			// points and bombdamage should be the same sign (the double cast of 'points' is needed to prevent overflows and incorrect values slipping through.)
@@ -5759,7 +5759,7 @@ int P_RadiusAttack(AActor *bombspot, AActor *bombsource, int bombdamage, int bom
 				dist = clamp<double>(dist - fulldamagedistance, 0, dist);
 				int damage = Scale(bombdamage, bombdistance - int(dist), bombdistance);
 
-				double factor = splashfactor * thing->GetClass()->RDFactor;
+				double factor = splashfactor * thing->RadiusDamageFactor;
 				damage = int(damage * factor);
 				if (damage > 0 || (bombspot->flags7 & MF7_FORCEZERORADIUSDMG))
 				{
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index d95bae5b2f..9ccdde24e3 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -312,6 +312,9 @@ DEFINE_FIELD(AActor, Conversation)
 DEFINE_FIELD(AActor, DecalGenerator)
 DEFINE_FIELD(AActor, fountaincolor)
 DEFINE_FIELD(AActor, CameraHeight)
+DEFINE_FIELD(AActor, RadiusDamageFactor)
+DEFINE_FIELD(AActor, SelfDamageFactor)
+DEFINE_FIELD(AActor, StealthAlpha)
 
 DEFINE_FIELD(PClassActor, Obituary)
 DEFINE_FIELD(PClassActor, HitObituary)
@@ -320,10 +323,6 @@ DEFINE_FIELD(PClassActor, BurnHeight)
 DEFINE_FIELD(PClassActor, BloodColor)
 DEFINE_FIELD(PClassActor, GibHealth)
 DEFINE_FIELD(PClassActor, WoundHealth)
-DEFINE_FIELD(PClassActor, FastSpeed)
-DEFINE_FIELD(PClassActor, RDFactor)
-DEFINE_FIELD(PClassActor, SelfDamageFactor)
-DEFINE_FIELD(PClassActor, StealthAlpha)
 DEFINE_FIELD(PClassActor, HowlSound)
 
 //==========================================================================
@@ -490,7 +489,11 @@ void AActor::Serialize(FSerializer &arc)
 		A("visiblestartangle",VisibleStartAngle)
 		A("visibleendangle",VisibleEndAngle)
 		A("visiblestartpitch",VisibleStartPitch)
-		A("visibleendpitch",VisibleEndPitch);
+		A("visibleendpitch",VisibleEndPitch)
+		A("rdfactor", RadiusDamageFactor)
+		A("selfdamagefactor", SelfDamageFactor)
+		A("stealthalpha", StealthAlpha);
+
 }
 
 #undef A
@@ -4105,9 +4108,9 @@ void AActor::Tick ()
 			else if (visdir < 0)
 			{
 				Alpha -= 1.5/TICRATE;
-				if (Alpha < GetClass()->StealthAlpha)
+				if (Alpha < StealthAlpha)
 				{
-					Alpha = GetClass()->StealthAlpha;
+					Alpha = StealthAlpha;
 					visdir = 0;
 				}
 			}
@@ -4828,8 +4831,11 @@ AActor *AActor::StaticSpawn (PClassActor *type, const DVector3 &pos, replace_t a
 	actor->renderflags = (actor->renderflags & ~RF_FULLBRIGHT) | ActorRenderFlags::FromInt (st->GetFullbright());
 	actor->touching_sectorlist = nullptr;	// NULL head of sector list // phares 3/13/98
 	actor->touching_rendersectors = nullptr;
-	if (G_SkillProperty(SKILLP_FastMonsters) && actor->GetClass()->FastSpeed >= 0)
-	actor->Speed = actor->GetClass()->FastSpeed;
+	if (G_SkillProperty(SKILLP_FastMonsters))
+	{
+		double f = actor->FloatVar(NAME_FastSpeed);
+		if (f >= 0) actor->Speed = f;
+	}
 
 	// set subsector and/or block links
 	actor->LinkToWorld (nullptr, SpawningMapThing);
@@ -6701,10 +6707,14 @@ static double GetDefaultSpeed(PClassActor *type)
 {
 	if (type == NULL)
 		return 0;
-	else if (G_SkillProperty(SKILLP_FastMonsters) && type->FastSpeed >= 0)
-		return type->FastSpeed;
-	else
-		return GetDefaultByType(type)->Speed;
+
+	auto def = GetDefaultByType(type);
+	if (G_SkillProperty(SKILLP_FastMonsters))
+	{
+		double f = def->FloatVar(NAME_FastSpeed);
+		if (f >= 0) return f;
+	}
+	return def->Speed;
 }
 
 DEFINE_ACTION_FUNCTION(AActor, GetDefaultSpeed)
diff --git a/src/scripting/thingdef_properties.cpp b/src/scripting/thingdef_properties.cpp
index 3838c3a89a..a6657ce972 100644
--- a/src/scripting/thingdef_properties.cpp
+++ b/src/scripting/thingdef_properties.cpp
@@ -1310,24 +1310,13 @@ DEFINE_PROPERTY(poisondamagetype, S, Actor)
 	defaults->PoisonDamageType = poisondamagetype;
 }
 
-//==========================================================================
-//
-//==========================================================================
-DEFINE_PROPERTY(fastspeed, F, Actor)
-{
-	PROP_DOUBLE_PARM(i, 0);
-	assert(info->IsKindOf(RUNTIME_CLASS(PClassActor)));
-	static_cast<PClassActor *>(info)->FastSpeed = i;
-}
-
 //==========================================================================
 //
 //==========================================================================
 DEFINE_PROPERTY(radiusdamagefactor, F, Actor)
 {
 	PROP_DOUBLE_PARM(i, 0);
-	assert(info->IsKindOf(RUNTIME_CLASS(PClassActor)));
-	static_cast<PClassActor *>(info)->RDFactor = i;
+	defaults->RadiusDamageFactor = i;
 }
 
 //==========================================================================
@@ -1336,8 +1325,7 @@ DEFINE_PROPERTY(radiusdamagefactor, F, Actor)
 DEFINE_PROPERTY(selfdamagefactor, F, Actor)
 {
 	PROP_DOUBLE_PARM(i, 0);
-	assert(info->IsKindOf(RUNTIME_CLASS(PClassActor)));
-	static_cast<PClassActor *>(info)->SelfDamageFactor = i;
+	defaults->SelfDamageFactor = i;
 }
 
 //==========================================================================
@@ -1346,8 +1334,7 @@ DEFINE_PROPERTY(selfdamagefactor, F, Actor)
 DEFINE_PROPERTY(stealthalpha, F, Actor)
 {
 	PROP_DOUBLE_PARM(i, 0);
-	assert(info->IsKindOf(RUNTIME_CLASS(PClassActor)));
-	static_cast<PClassActor *>(info)->StealthAlpha = i;
+	defaults->StealthAlpha = i;
 }
 
 //==========================================================================
diff --git a/wadsrc/static/zscript/actor.txt b/wadsrc/static/zscript/actor.txt
index 9796c3e8df..2fc0d6d3bd 100644
--- a/wadsrc/static/zscript/actor.txt
+++ b/wadsrc/static/zscript/actor.txt
@@ -190,6 +190,9 @@ class Actor : Thinker native
 	native voidptr /*DecalBase*/ DecalGenerator;
 	native uint8 fountaincolor;
 	native double CameraHeight;	// Height of camera when used as such
+	native double RadiusDamageFactor;		// Radius damage factor
+	native double SelfDamageFactor;
+	native double StealthAlpha;
 
 	native meta String Obituary;		// Player was killed by this actor
 	native meta String HitObituary;		// Player was killed by this actor in melee
@@ -198,8 +201,6 @@ class Actor : Thinker native
 	native meta color BloodColor;		// Colorized blood
 	native meta int GibHealth;			// Negative health below which this monster dies an extreme death
 	native meta int WoundHealth;		// Health needed to enter wound state
-	native meta double FastSpeed;		// speed in fast mode
-	native meta double RDFactor;		// Radius damage factor
 	native meta Sound HowlSound;		// Sound being played when electrocuted or poisoned
 
 	meta Name BloodType;		// Blood replacement type
@@ -212,6 +213,7 @@ class Actor : Thinker native
 	meta Sound MeleeSound;
 	meta double MissileHeight;
 	meta Name MissileName;
+	meta double FastSpeed;		// speed in fast mode
 
 	Property prefix: none;
 	Property MeleeDamage: MeleeDamage;
@@ -222,6 +224,7 @@ class Actor : Thinker native
 	Property ExplosionRadius: ExplosionRadius;
 	Property ExplosionDamage: ExplosionDamage;
 	Property BloodType: BloodType, BloodType2, BloodType3;
+	Property FastSpeed: FastSpeed;
 	
 	// need some definition work first
 	//FRenderStyle RenderStyle;
@@ -290,6 +293,11 @@ class Actor : Thinker native
 		VisiblePitch 0, 0;
 		DefaultStateUsage SUF_ACTOR|SUF_OVERLAY;
 		CameraHeight int.min;
+		FastSpeed -1;
+		RadiusDamageFactor 1;
+		SelfDamageFactor 1;
+		StealthAlpha 0;
+		
 	}
 	
 	// Functions