Backing may or may not be neccessary- based on the quality of the stave (board) and the design of the bow, the quality of workmanship in its making,etc. etc. The wider the limb the less susceptiable to breakage, how true the grain runs, the amt of poundage desired etc. etc. Why not just back it w/ silk? Its light, its organic, easy to do, and readily avaiable. Just go to any Good Will store or factsimilie thereof, and find your self a silk tie, or shirt - whatever. Glue it to the back with Titebond 3 and forget about it. You can paint it, put designs on it whatever. It will look great, and it will last. Let the kid paint it with his own design. Indian patterns look good, and are easy to paint. I use acyrlic paint. Paint the backing solid black, and then use yellow, white, red etc. for patterns. With the Black background, yellow and red is quite striking. Good luck.