rduff,

Balsa USA should still sell the build manual and plans. If you do a search, you will find some threads here on the subject that will help you out. I had an Enya 120 4-stroke in mine and it was over powered, but nice. It did take some ozs of lead to balance though. I think a strong 90 4-stroke would do well. I have 1/4 scale Cub wheels on mine and it looks right.

Have fun with it!

Bedford