My friend (the one who has the Bull Smoker for sale) is wanting to build a New Insulated Smoker A pit inside a pit made out of steel to fit inside an inclosed trailer. I know there are several Pit makers who use this design. Some of the questions I have is what type of materal is best to use for insulating, how thick, does the outer box need to be vented? sould the firebox and the smoke chamber both need to insulated, what about the doors. Any Information would be appreciated.