JustinJ ; Well I am a bit opinionated about Powell's as I once was a dealer for that line of bikes. And the frame design is very strong but not overweight. One factor is the working suspension that takes the shock and stress of heavy off road riding. And the large wheel size gives the bike a good ground clearance.
If you look into my picture section there are numerous articles about the Powell and it's evaluation . As for improving a tried and true machine just think about that. I has a mono sprung swing arm and absolute dead on chain alignment a thing that most mini bikes with jack shafts do not have. Being that the pivot of the swing arm is also the drive sprocket mount. That is on the Phantom 7 series.
Here to help in any way. Steve