Put a Myers comb on it and Graco adjustable pad and you don't have to mess with bending.
Yes this will change the dimensions but it will also add considerable weight and change the balance noticeably, usually resulting in different handling characteristics. an improvement, maybe a disaster. Quite a few real gunsmiths bend stocks, especially ones that regularly work on fine doubles and they can do some amazing things but there are several things to consider…
It will be at your risk. The gunsmith will specify that if the stock breaks he takes no responsibility. Every piece of wood is individual, different, unique. If it turns out to be brittle, have internal flaws that can’t be seen, etc it can break. Your risk, not the smith’s.
There is a possibility of this process damaging the stock finish and in this case the matter of a stock refinish and maybe checkering touch up at the owner’s expense must be addressed.
This is a hot, dirty, smelly process, most smiths only do it in the summer, outside.
Cost will range from $300 tp $450 these days.
Bending a stock up or down isn’t practical with a traditional side by side because the top and bottom tangs would also need to be bent and then they wouldn’t quite fit the inletting properly but it can be done on some modern shotguns with a through bolt attached stock.
Another option on a Beretta might be to source a new Beretta Vittoria stock.