This might belong in pow-wow?
Brace height can make a difference, but most guys set brace height in order to tune the bow, not to avoid string slap. Ever heard a wheelie guy complain about string slap? It almost never happens with compounds because the brace heights are much higher than they are on most trad bows.
If you can raise the brace height w/o sacrificing tune it's worth looking into imo.
That said, usually grip is the problem. Try rotating the heal of your bow-hand away from the riser a bit. Your elbow will rotate a bit with it and that may be all you need.