I think cheek slap is largely a product of not enough drop at the comb, along with too square a transition to the rollover part If there isn't enough drop, then you are forced to cant your head to get a sight picture, and the corner of your cheek bone is against the corner of the rollover. If the dish in the cheek piece isn't that great, then that also forces you to cant your head.
Plus, if where you mount the gun still has a lot of upward angle heading toward the breech, when the gun comes back that will raise the comb too. My last Lehigh was a Stophel Long semi-carves one I got from Dave Keck in 50 cal.. All of the above were present. It acts mild enough up to about 55 gr, but much above that and about 4 shots is all I can take before a bruise starts developing. I would still hunt with it and use 110 gr charges though. 1 shot and 1 slap per season isn't that big of a deal. At the range it is though.
My current build is a Jacob Kuntz in 38 cal with a 48" A-weight barrel. I'm going to be hard pressed to load it up enough to make an 83 gr. ball generate enough recoil for any kind of a slap, even if it's prone to want to. That said, I DID put a bunch more drop in it at the comb, so that I could mount it with my head erect and sight it more easily. Those low original sights are not easy to use even in the best of circumstances.
