Concord Model Engineers had a nifty little indoor combat flyer, christened the Piranha. I stupidly didn't take a picture of the plane, but it's in the background. I'll take some more pictures at the next CME indoor fly... I want to build one!
Stats as I recall them: 24'' wingspan, 3oz. (!) 6mm EPP, 2.5g servos, HK AP05 motor, 5x3 prop.
Mike builds his own small, lightweight 3S batteries out of ZIPPY 240mAh 20C single cells. He solders the three cells together, tab-to-tab and attaches a mini-JST connector. It looks like lightweight medical tap holds everything together, and attaches velcro as necessary. Zoom in to see exactly where the tabs are being soldered. He doesn't bother with balancing. Battery weight: [[[???]]], contrast with Turnigy Nanotech 3S 370mAh at 39g.