Regular gygax can only fit nonlethal weapons.

code/game/mecha/combat/combat.dm

@@ -3,6 +3,7 @@
 	var/melee_cooldown = 10
 	var/melee_can_hit = 1
 	var/list/destroyable_obj = list(/obj/mecha, /obj/structure/window, /obj/structure/grille, /turf/simulated/wall)
+	var/maxsize = 2
 	internal_damage_threshold = 50
 	maint_access = 0
 	//add_req_access = 0

code/game/mecha/combat/gygax.dm

@@ -15,13 +15,14 @@
 	wreckage = /obj/effect/decal/mecha_wreckage/gygax
 	internal_damage_threshold = 35
 	max_equip = 3
+	maxsize = 1
 	force = 10
 
 /obj/mecha/combat/gygax/loaded/New()
 	..()
 	var/obj/item/mecha_parts/mecha_equipment/ME = new /obj/item/mecha_parts/mecha_equipment/weapon/energy/taser
 	ME.attach(src)
-	ME = new /obj/item/mecha_parts/mecha_equipment/weapon/ballistic/missile_rack/flashbang/clusterbang
+	ME = new /obj/item/mecha_parts/mecha_equipment/weapon/ballistic/missile_rack/flashbang
 	ME.attach(src)
 	return
 
@@ -37,6 +38,7 @@
 	overload_coeff = 1
 	wreckage = /obj/effect/decal/mecha_wreckage/gygax/dark
 	max_equip = 4
+	maxsize = 2
 	step_energy_drain = 5
 
 /obj/mecha/combat/gygax/dark/New()

code/game/mecha/equipment/weapons/weapons.dm

@@ -4,18 +4,20 @@
 	origin_tech = "materials=3;combat=3"
 	var/projectile
 	var/fire_sound
-
+	var/size=0
 
 /obj/item/mecha_parts/mecha_equipment/weapon/can_attach(var/obj/mecha/combat/M as obj)
 	if(..())
 		if(istype(M))
+			if(size > M.maxsize)
+				return 0
 			return 1
 	return 0
 
 
 /obj/item/mecha_parts/mecha_equipment/weapon/energy
 	name = "General Energy Weapon"
-
+	size = 2
 	action(target)
 		if(!action_checks(target)) return
 		var/turf/curloc = chassis.loc
@@ -107,7 +109,7 @@
 	equip_cooldown = 8
 	projectile = /obj/item/projectile/beam/stun
 	fire_sound = 'sound/weapons/Taser.ogg'
-
+	size = 1
 
 /obj/item/mecha_parts/mecha_equipment/weapon/honker
 	name = "HoNkER BlAsT 5000"
@@ -169,7 +171,7 @@
 	name = "General Ballisic Weapon"
 	var/projectiles
 	var/projectile_energy_cost
-
+	size = 2
 	action_checks(atom/target)
 		if(..())
 			if(projectiles > 0)
@@ -343,7 +345,7 @@
 	projectile_energy_cost = 800
 	equip_cooldown = 60
 	var/det_time = 20
-
+	size=1
 	action(target)
 		if(!action_checks(target)) return
 		set_ready_state(0)
@@ -361,7 +363,7 @@
 	name = "SOP-6 Grenade Launcher"
 	projectile = /obj/item/weapon/grenade/flashbang/clusterbang
 	construction_cost = list("metal"=20000,"gold"=6000,"uranium"=6000)
-
+	size=1
 /obj/item/mecha_parts/mecha_equipment/weapon/ballistic/missile_rack/flashbang/clusterbang/limited/get_equip_info()//Limited version of the clusterbang launcher that can't reload
 	return "<span style=\"color:[equip_ready?"#0f0":"#f00"];\">*</span>&nbsp;[chassis.selected==src?"<b>":"<a href='?src=\ref[chassis];select_equip=\ref[src]'>"][src.name][chassis.selected==src?"</b>":"</a>"]\[[src.projectiles]\]"