Looking at building a custom rear mount tank for this build. I would like to keep the top bar clean looking. All the round tanks are way to expensive, even the vintage ones on ebay. Sooooooo I was thinking, if a small propane tank can hold pressurized propane, why not gas? I will utilize a marine vent cap for the gas tank, as the cap. It has vent holes in top with screen. I will use JB weld to secure the nut to a hole I have drilled into tank. Then the vent cap will just screw into secured nut on propane tank. That way I can unscrew to filler up, using a funnel. I hope this works. Here's the general idea anyway.