im doing a shoe box size rack what size flexwatt should i use fo underbelly heat 3 in or 11 i have toons of the 11in none of the 3 i dont wanna do back wall heat at all dosnt heat well enough in my opinion its for my balls that are hatchling to near yearlings so i already had a respertory problem once im not leting my lil guy down ever again with not enough heat please help...ps im use painted ply wood heat coated my dad help me with hes a carpenter so its cool with side walls and backin if that help because i see alot of people useing stuff with no back or sides anheat is wasted.