RC, i used a 14oz spare tank out of my ucd60 and i enserted the tank in aginst the firewall right up aginst the support beam that runs across the inside of the firewall and then marked the tank on the inside (also put red lipstick on the hole and cut it out) then i build a support for the bottom of the tanki and then i built a support for the rear of the tank(what you see in the picture below, is real stable and pretty easy to build and support.