If I knew the solution I would share it, but I currently am trying to solve my own proplem with glasses I just picked up on Thursday and most everything is slighly out of focus.
One problem that I had was these leetle lenses on the glasses my wige chose for me a couple of years back. When I established a cheek weld, I found myself looking over the top of my glasses. The new ones have larger aviator type frames and that helps.
I may have this all wrong, but for flying targets, be they clay of feathered, you don't use your sights. I have been told time and time again that if you look at the barrel or the bead you are going to miss. I will let the smart guys explain that one.
If you are shooting a stationary target, like deer, I believe you may want to use sites and even a scope. I don't know.
BTW, my gun is an 870 Express that I bought with a police type barrrel and corn cob forearm and I later added a 28" field barrel.
Call me half blind in California.