Morning GG, yes back seat is the fuel tank. Have had a few question this set up, ( regarding sitting on a roto molded fuel tank ) I have then asked do you ride a quad, answer yes, whats the tank made from, end of concern. You are not wrong about the old 3 wheeled ATV's, deadly. Could be tradition, not many 4 wheeled aircraft about, less drag, better visibility from the front seat, who knows. Will post some more photos as I go, the back wheels are not the right ones have tundr's to go on eventualy.
Cheers Tim