Bill: Ok, but 30 minutes, is probably shorter than what you plan to fly. Practice the mission, fly what you practice!
Kerry: 20 minute duration is what I am aiming for.
Bill: Ah. Like my evening "quick fix " flights. From 15-30 minutes. Depends on conditions of course. My plan is for max 1 hour flights.
Kerry: Exactly, purely a pleasure craft. With the current state of batteries it will be hard to have much more duration and still meet the "5 gallons of fuel" ultralight limit. 
Kerry: Even without that limit, adding more range makes the problem exponentially harder. 1 hour can be done but it won't be easy.
Bill: That's where using a "motor floater" design is superior. Get up there, turn it off and seek thermals. Just use it to go thermal to thermal. Or get back to the runway.
Kerry: Ah yes, completely agree. 
Kerry: A self launch motorglider is a real good option. It also helps get around the 30 minute min fuel reserve requirement.
Kerry wants to fly 20 minutes on motorglider. Bill aims for 1 hour flights maximum.