RE: 1/4 Scale Balsa USA J-3 Cub
Caley,
Your cub will be approximatly the same size as the Hanger 9 cub. I know that there are several power systems that will fit it. If you order your components from Hobby City, you should be able to come in for less than $300 for your entire system. If you were to want an extra battery, you would want to add about another $100 depending on which capacity you choose. A friend of mine built his 94" cub and only has $200 in his power system. Good luck on this project.
Darrell B.