thanks for the info, looks like it turned out great! i wound up using two 1lb propane bottles, cut the curved tops off and welded them together, hacked off a fill from a stock tank etc.. if you look around you can find the propane tanks with the flat bottom at wally world, the coleman tanks have a funny shape on the bottom covered with a plastic cap i didnt like those, if i get a chance this week ill post a pic.. its about 4 and 1/2 inches in dia. and i made mine 12" long to fit behind my seat or upper frame rail, havent decided which yet. Have fun!
ps: please make sure the tanks are completely empty before you start drilling and cutting, i submerge the empty tank and drill bit in a bucket of water while i drill the start hole, the water prevents heat and sparks from the drill, then i hacksaw them to the length i want. you could braze and solder them together also. havent tried jb, but who knows! a cheap tank for sure! $4.00