Sorry you're getting your "cheek slapped" -- I'm not up to speed on all the stocks available these days, what's an RST? The Blachawk site shows Knoxx recoil reduction stocks in two basic types: The SPECOPS where your face and shoulder are isolated from recoil and the COMPSTOCK where just your shoulder is isolated but not your face. Is the RST like the COMPSTOCK?
I have a JS Air Cushion stock on a Skeet gun and a Shockmaster on a Trap gun. Both of these provide recoil reduction for the face and shoulder. I imagine a COMPSTOCK-type unit could easily slap you face significantly if not properly fit to the shooter.
If your cheek is taking a beating, you might get some temporary relief by applying a pre-shave talc stick to your cheek before you shoot.
A more horizontal pitch may help -- you could try shimming the stock.
