So, it was last summer when I was messing with fixing the air-hogs Aero-ace airplanes. From what I remember, I was somewhat successful at getting the new batteries installed and charged. My problems came from the batteries being too heavy, and not getting much more than a somewhat controlled glide out of each plane even at full throttle. It was fairly discouraging, and at the same time, my friend had made a foam board RC airplane that was much more fun to fly. (Not too surprising).
I decided not to mess with them much more after that. I assume that there is a lipo that is fairly easily available that would work, but for me, it just wasn't worth it anymore. The larger, but more maneuverable, foamy really inspired me to finish the laser cutter to make more foam RC planes.
Who knows, I may return to these, they are still sitting on a shelf in my garage. Flite test has done some cool video's on micro RC planes in the past, and these air-frames would be perfect for the same micro control electronics.