Im going to be making my first smoker trailer with this old propane tank not sure the exact size guessing 120 gallon and a 16ft trailer I do have a few questions on some things before i get started ...i will be making it into a RF smoker and one question is what thickness should i use for the firebox and also the size i should use for the RP on the inside...and as far as the trailer what kind of floor would be a good idea to go with ....tyi everybody