RE: Super Cub LP wont balance
What battery are you using?
After reading your first post again I see that it has a custom battery box and it sounds like the designer didn't get the COG right. That means you probably need to move the battery more forward.
Oh, and never believe the previous owner from Ebay.
This video is very informative. It also says 2.25" from LE.
[youtube]http://www.youtube.com/watch?v=kq2VeC9-n9Q[/youtube]