Off the rack shotties don't fit me well either (at least not the ones I like), so I have used two solutions:
1. I bought a synethetic stocked Beretta with shims and a selection of LOP spacers and adjusted LOP, cast and drop to fit me.
2. I sent both of my wood-stocked Beretta OUs to a gunsmith in Quebec to have the stock steam-bent to fit me. He guided me through taking measurements at home (with help) and I sent him the first one without actually going to see him. It fit me perfectly by the time he was done with it. When I bought a second, more expensive, OU, I took advantage of a trip to Montreal for other reasons to actually go and visit him and have him re-measure me in person. The measurements that he had me take at home and the ones that he took in the store ended up being VERY close - nearly identical. He steam bent that one for me too and it also fits me perfectly, of course. He charges 150$ for steam-bending, including the measuring and all that of course, which I think is VERY reasonable. The cost of cutting the stock to adjust LOP was extra, and varies depending on the cost of the recoil pad that you want. In my case I wanted a fairly expensive recoil pad added so it and needed a shim as well so it was 210$, but that cost would likely depend on what you need done exactly (shorten? Lengthen? keep existing pad? etc...). Anyhow, I have been very happy with the work that he's done for me (I've had other stuff done as well - all great work). Alain Combes just north of Montreal
http://www.armurier-quebec.com/indexgb.html Once you've had shooties that shoot where you look you'll never go back.
He speaks good English, by the way.
-Dave