Try one in a lightweight youth model break-open single shot, that doesn't have a recoil pad
The recoil is no different with same weight of TSS than with same weight of lead.
1 1/2 oz is 1 1/2 oz with either.
Any recoil difference is related to something other than TSS.
In my 12 gauges, before TSS, I was shooting 2 oz lead loads coming out at @ 1300 fps.
With TSS, my load is typically 1 3/4 oz TSS coming out at @ 1200 fps.
So in that comparison, "my" TSS loads there have noticeably less recoil than the heavier, faster lead loads.
In my 20 gauges, before TSS, I was shooting 1 1/4 oz lead loads coming out at @ 1100 fps.
With TSS, my load is typically 1 1/2 oz TSS coming out at @ 1100 fps.
So in this comparison, the TSS loads have greater recoil than my former "lighter" lead loads.
Interestingly, it's still not "felt" as hard as the heavier 12 ga guns with a 1 3/4 oz load.