Grip the barrels, not the forearm. This theoretically gets the hand in a better plane with the barrels for the shot. Winchester 21s have beavertails and most other doubles can be purchased that way as an option. I prefer a beavertail on my 28 ga guns since the barrels are a lot smaller and so there's less to grip, as well as fingers can overlap getting in the way of seeing. I'd shoot both splinter and beavertail before I made a decision.
Joe