Owen,
You mentioned that your SxS's are fitted for you. Is the O/U fitted as well? You said that easing the cheek pressure causes you to miss birds, possibly resulting in the incorrect drop at comb/face.
I have one SxS that is stocked just a wee bit high, requiring me to cheek harder to get the correct sight picture. No bruising as it's a 28 ga. I normally cheek the combs on my other ones with medium/comfortable pressure. Drop at heel and stock pitch can have a great affect also.
Hope this helps,
Karl
