RE: Recoil Question??
#1. you don't have to shoot 3.5" shells when you go goose hunting. A 2.75" 12 ga shell will hold the same weight shot as a 3" 20 gauge shell. Choose a smaller size shot for a denser pattern at longer ranges... maybe something likeheavyshot #2's.
#2. A 12 gauge gun will be heavier than a 20 gauge gun of the same make and model so the extra weight will help with recoil.
#3. You didn't say what shotguns you have but you should be able to install at least one mercury recoil reducer in the gun and probably two. One in the stock and one as a mag tube cap.
#4. you can get any make of recoil pad for as shotgun as you can a rifle.