I've never considered the PTR91 to be a rifle with excessive recoil in the traditional sense of recoil (my shoulder never hurts from shooting it). That said, with a proper cheek weld, the thing makes me feel like I'm getting punched in the face about 1-2 inches below my eye. I've already installed a muzzle brake, and while effective at controlling muzzle rise and normal recoil, it does absolutely nothing for the slamming sensation against my cheek bone. What solutions are available for this?

A better buffer :http://www.triggerwork.net/hksbuffer.html

And a HK 21 rubber butt pad to replace your plastic one.

Increasing the bolt gap a bit for some reason reduced the recoil on my G3 clone.

With proper shooting position and check weld there should be no slamming into your cheekbone feeling. You and the rifle should recoil as one.

The only weapon I have experienced cheek slap with was a Knoxx stock equipped shotgun but that was due to the design of the stock that allowed it to move back and up.

I would check your bolt gap and your locking piece.