Just won't do it again. First off, right out of nowhere, some kind of inclusion (can't figure out what) whacked my pattern cutter bit and chipped a cutting edge. :( . The inconsistency of the material made it difficult for the bit to cut an even smooth surface. Ended up doing a filler job on the back side surface just to get it smooth.
There's something in the composition of that stuff that makes any sliver in the hands flare up like crazy. This is the second form from this same sheet of OSB. The first one was a flat backed American Flatbow design that circumvents most of those cutting problems.
The nice thing about this stuff was when I purchased it, it was exact dimension 3/4". Two pieces made a perfect 1 1/2" form. These pieces, after sitting in my shed for about six years turn out to be more like 13/16ths inch. I can deal with it but prefer not to!
So my next form (will be a one piece recurve) will be made from the laminated lumber that has gotten so many raves here.
Live and learn!