Lloyd,
My only remaining guns are now SxS's with double triggers. I noticed the same when I started to use them exclusively. I started to use the Grip Swell SxS gloves which seemed to have padding in all the right places, the middle finger included. I shoot 1 oz. and 7/8 oz. loads at 1170 & 1200 fps. as well in my 12 ga. guns. The big difference I've found was hand position. I set up my grip for the back trigger and simply reach forward to the front trigger for the second shot. It helped a lot and the problem disappeared for me, so I believe that initial grip set up is the key. My stocks are all straight gripped.
Hope this helps,
Karl
