Is your gun a true trap gun or just a generic Silver Pigeon? Does it have an adjustable comb. 55/45 is a little low for a trap gun, I shoot 60/40 from the 16 and 90/10 from handicap.
Trap is tough because unless you are shooting consistent 24's and 25's it's hard to place when competing. There are other things you could be doing that are affecting your scores that have nothing to do with the gun, stopping the gun instead of following through on the angle birds is just one, foot position, not keeping your head on the stock, dropping your arm and pulling the gun away from your eyes is common. Are you sure which is your dominant eye?
Guns are usually the least of the problem, I've run 25's with field guns and antique guns, whatever I shoot my technique is the same and just have to change if I cover the bird or not depending on POI, most field guns shoot flat.
If you shoot at AGC I would be happy to meet you up there and see if I notice anything, also happy to let you try my trap gun to see if it makes any difference.
I"m a member of AGC but have never shot trap, when is the best time to show up where there are people willing to help? Any idea on what it costs for an instructor? I'd be interested to pay someone to meet me and my son on say friday lunchtime if that could happen. He is done with school by then and I can often take a long lunch. I had also thought about going to PG Trap & Skeet to do the same if they have instructors that work out of there. I have no clue how much trap I would shoot but don't know until I try it and figure It could only help my bird hunting skills as well which are at a novice level.