Ok, since it's a foam glider, try this. Without any equipment installed check the present CG by the method the "thstone" said, with an index finger under the wing on each side of the fuse. Find the point where the glider balances, fore and aft. Mark that point under each wind and use it as a reference point, then as you add components you want to maintain balance at that point or slightly to the rear so you have a slight down nose angle with everything installed. The object is to be just slightly nose heavy. Instead of using your fingers you can take a 2" x 6" piece of wood maybe 2' long and drill two holes about 4" each side of center (8" apart) and make the holes just large enough to insert wood pencils with an eraser on the end. Sharpen or round the eraser slightly and use those instead of the fingers. Then your hands are free and you can "play" around and find the CG on a bare glider and work from there. Don't know how successful you will be converting a foam glider. You may want to consider buying a ready to fly electric airplane with at least a 3 channel radio. A lot less headaches.