When you say Concave are you referring to a swamped rib. There is a major difference between a concave & a swamped rib. I have had several guns with concave ribs. Never had a swamped rib, though I always wanted to try one.
As I was always a hunter rather than a clays shooter, the standard SxS configuration is my Favorite & can use either a flat or concave rib with no discernable difference. Don't want no rib stuck up on stilts looking like a trestle bridge. I also prefer two triggers on a two barrel gun. As a matter of fact, I'm so ate up with Old Fashioned I even prefer an auto-safe.
