I am in the beginning stages of building a BBQ Concession/Catering trailer. I am building one styled after the Southern Yankee BBQ Shack trailers. The trailer I have is a 14' long (I may extend it a bit and move the axles not too sure yet) The split up I'm thinking is 5' for the smoker open area and 9' for the enclosed kitchen area. I'm planning to build my own smoker/cooker but not sure what size to go with. I'm leaning toward using a 120 gallon compressor tank (74"L and 29"D) with an offset firebox reverse flow design. Do you guys think the 120 gallon tank will be too small?? That 2146 sq cooking area on 1 shelf and slightly less on the upper shelf so with 2 cook shelves in it thats around 4000 sq cooking area. (top shelf removable so I can still roast a pig as well.) Looking at doing a few local Festivals and also Catering. I already talked to the health dept and they say as long as the materials for the cooker are non-porous and have not been used for chemicals or petroleum based products I should be ok. I do have to submit detailed drawings and a list of materials for the build to them for their approval.