Kinkster,
You could go even shorter if you eliminated the stiff handle and fadeouts. With a good piece of hickory board, you could go 1 3/8" wide in the middle and down to 1/2 inch wide tips with only 50" of bow length. Keep your cross section rectangular, and the tiller can be the tiniest bit stiff thru the handle area. If you back it with rawhide, it would be as good as indestructable (unless I get my hands on it, mwahahaha).
Getting used to the feel of a bow flexing in your hand after shooting stiff handled bows takes some getting used to!