The guns that I chose to have adjustable combs installed on fit quite well, but not quite perfect, so I wanted to fine tune them, to see if it would make a difference in my scores. I didn't really notice any significant difference in my scores after the combs were installed. Other shotguns that I shouldered were not even close to fitting, and a couple did not even have enough drop at comb despite the comb being adjustable. If the stock does not have enough drop at comb, it's not simply a matter of adding moleskin or duct tape, you actually need to remove material to make them fit, and with a cheap plastic stock, that isn't easy to do. As far as choosing a shotgun for clays, the odds of success drop off dramatically when the shotgun is not pointing where the shooter is looking, so why not choose a gun where the gun points as close as possible to where the shooter is looking, rather than just choosing a random gun, with no concern for how it fits?
As far as misses go, according to the scorecard, it's not a miss if the target breaks, and the difference between the target breaking or not when a decent shooter misses, is usually inches, especially with the small gauges.. Even clean rounds don't mean that the shooter was perfect they just mean that he was close enough.
Did you actually do POI testing on the shotguns before and after the comb install?
If you can reliably tell us how to get brakes on the fringes of our patterns those of us that actually compete will be all ears. Until then those that know will strive to shoot the hot core of the patterns rather than spray and pray.