HEy Donnie,
Try shooting longer arrows, maybe 28 or 30 inches even. I have a very short 36" Hupa replica bow that I made a few years back and I found that a 34" rivercane arrow flew the best off of it. It didn't have any bow slap and I was surprisingly accurate with it at 15 yards. Those shorter bows just seem to work better with longer arrows.
I saw a short Pitt River bow in the Smithsonian a few years ago, and the accompanying arrows were about 33-34 inches long, so the natives also knew that long arrows work better on short bows.