I grew up shooting my grandfather's FN A5 in 16 ga. from the "wrong" side. But is worked well for me because the safety was the ambi "front/back" design built into the forward bow of the trigger guard, and the stock didn't have any cast-off.
IMHO stock cast-off is the biggest handicap for a LH shooter stepping behind most RH shotguns. The mechanics of most SXS guns don't handicap a LH shooter, but the stock cast can.
Years ago I found a Merkel M8 12 ga. with a true left-hand stock (including the raised cheek-piece on the right side). Neither the triggers or lever were different from a RH gun. It is now my go-to in sporting clays contests, where sometimes I finish in the top 10%. It really fits me well and the cheek piece seems to help both cheek weld to the stock, and to distribute recoil.
