I have to emphasize here how important fit is. A more correct term would be "match" rather than fit. It doesn't matter as much how the gun feels as how it shoots. If it shoots where you are looking, you and the gun are a match.
When I was looking for an O/U shotgun, I tried shooting the Citori. It was a beautiful gun, well made, and it felt nice handling it and shouldering it. But everytime I shot it, it would shoot high from where I was looking (aiming if you will). I liked everything about the gun, but I could not get used to it shooting high. So I passed on it.
Later I had a hankering for a Winchester 101 XTR Lightweight for some reason, so I bought one. Like a dummy, I never shot a 101 before I bought one. Guess what? That gun shoots consistently to the left. No problem with right-to-left crossing targets, but left-to-right ones give me problems. Why? Because the gun has too little cast off to match me. It is a beautiful gun, smooth as silk to shoot, and I really wish it shot where I pointed it, but alas it does not. I still have it, but should probably sell it.
Then there is my Savage Fox Sterlingworth (SxS). I bought it and immediately took the stock off, went to an English gunsmith in Canada, and using a try gun had him give me my dimensions of fit. I then made my own stock and set the length of pull, cast off, drop at comb, and drop at heel for my body. Guess what? It shoots dead on every time. The gun matches me.
Most people will not bother to restock a gun to their dimensions, but you really should shoot anything you are thinking of buying to see if it hits where you point it. I can guarantee you if you buy a good quality double that matches your body, you will have a friend for life. I do not think I will ever sell the Fox.
Lou