So I'm guessing you are talking about this plane:
http://hobbycity.com/hobbyking/store...dproduct=12617
I don't know if you can use a 4S pack without frying something. That would be 33% more than the recommended voltage. To me, that just seems foolish, but perhaps someone else will jump in with more information.
My question is: Why don't you want to use the recommended 3S pack?
- Jeff