As far as flight time goes you're probably not going to be able to get anymore than about 20 mins of power time from a typical battery.

Have you thought about going with an electric glider? Not as aerobatic as some of the sport planes but they'll get you up in the air and if you can find good air you can stay up for hours. Plus if you start getting low you just hit the throttle and take off for another 30+ min flight. Just a suggestion though