For what its worth, I installed a grind to fit Limbsaver pad on my 12 and shot this weekend. I think I ran 30 shots through it and can tell you the recoil is not an issue at all. Yes, some slugs have a little more punch (Lightfields), but not anything i would think anyone would develop a flinch from. The recoil is a fraction of what my turkey gun (870) is.
On a side note, the grind to fit pad is actually pretty easy if you have a belt sander. Just take your time and it should come out pretty good.