You should be able to close your eyes, mount the gun into the zygomatic arch, and that's your perfect mount. Open your eyes. Are they straight down the rib?
I have come to believe this is not entirely true. I can take a gun that fits my hunting style dimensions 1 3/8 to 1 1/2 at the comb and 2 5/8 to 2 3/4 at the heel (or within these relative dimensions) close my eyes mount it a few times and after that it perfectly aligns. I have a Charles Hellis made for a lefty and can do the same. Let me shoot it for a round to warm up and off I go. That is my hunting scenario for I rarely shoot the same gun twice in a season except my Citori that I use for migratory. Something else is going on and I can't figure it out.
The first thing a gun fitter will do is to teach you how to properly mount a gun. Then you will need to be able to do it every single time. Requires a lot of practice. Then he can start making adjustments to the stock, pattern it, adjustments, pattern it, adjustments, etc.
I have so many shotguns, I don't bother getting them all fitted. My SXSs I certainly will not have fitted, because I do not want any modifications done to the stocks. Sidelocks shotgun stocks require hot oil and bending, which is the correct way to do it, but a pain in the ass, because you have to bend the tang and trigger guard along with it. The only shotgun I have fitted to me is my Kreighoff K80, because it's built like a tank and it's easy to fit. I'm currently on the lookup for a nice side lock hunting shotgun, which I will have fitted as well. That way I can have a competition sporting clays gun fitted and a hunting shotgun fitted. Until then I will use my K80 for everything. For example, in the CA state shoot last week, I shot my SXS and scored about 35/100. I shot my K80 (which was fitted) and scored 60/100. I know that K80 fits me like a glove and always points to where I look. That's myself in the picture above. I am working with Dale Tate and he does a great job fitting a shotgun.
