Re: Gas tank and exhaust questions?
Many vendors offer larger tanks that what comes with the basic kit. You might also explore local salvage yards for a motorcycle tank that could be adapted to your top tube. See if you can locate a Yamaha MX 80 tank. I too used a Suzuki Junior tank but the one I had was steel, not plastic.
Lots of options to choose from for a fuel tank. Fruit/soup cans, thermos bottles, fire extinguishers, and the list is as varied as the imagination and innovation of the members here.
Use your imagination and let us know what you come up with.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"