A Piper Cub is a good full scale trainer, but not a very good RC trainer. You need a specifically designed RC trainer.

These are good trainers and if you search, you'll find more. You never know what you are getting from eBay in the way of Almost Ready to Fly planes. Some of the kits are really bad.

Here are some good links to trainers:
[link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=HAN2450]Hangar 9 Alpha[/link]
[link=http://www.horizonhobby.com/Products/ProductGallery.aspx?ProdID=HAN2475]Alpha Combo[/link]
[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCAS2&P=ML]Tower Trainer[/link]
[link=http://www.hobbypeople.net/gallery/159841.asp]Wasp Trainer[/link]