RE: Best way to find CG?
The book tells you where its at, just measure that far back on the wing put some marks with a sharpie or something and balance it with 2 pencils, your finger tips, whatever.
On my cessna it didnt really need any balancing, I just put the stuff in and it was balanced just right. When using the stock battery theres really not alot of balancing you can do as the battery can only move an inch or so either direction.