If you are building something for the cross country gig, I would build something sleeker than a bipe. Then use a high pitch prop and between that and the aerodynamics, you would be able to throttle way back and save fuel. I would think an hour would be feasible in such a case without a very heavy load of fuel. Probably doable on 16 oz.

I'm thinking about doing a 60 mile cross country, but I was just going to hang a 32 oz. tank on my Giant Stik with a Poulan 42cc on Gas/Glow, (in addition to it's normal on board tank of about 12 oz.), and go for it...

AV8TOR