Now that I see the pics of your trapper, Salvo, it makes me want to weep at my own short-sightedness. About a year ago I stopped by a gunshop that's not particularly into lever guns, and passed up an angle-eject 30-30 with one of those safeties, and which had some rust-pitting. In decent shape otherwise. I thought to myself "truck gun", since they were only asking for $185. I figured I'd find another around the same price, but maybe of the vintage just before those safeties. When my gunsmith buddy said he could make a plug kind of like your design, I went back, a couple of days later. That Winnie was gone.
I've never had a problem with my rebounding hammer, and have fired my 44 cal trapper extensively, mostly with cast bullets. Nice to know it can be switched over to a half-cock though. With my carbine my biggest gripe always was the lever link. It's always been too narrow at the wide parts at the front and back for the opening at the bottom of the receiver, making for a kind of wobbly lever arrangement. That's really not a function problem-except for maybe a tendency to rattle in the woods. Mostly I've used tighter Winnies when I seriously hunt. I expect that with my trapper, somebody at Winchester either machined the lower opening in the receiver a bit to wide, or I got a link that was machined a bit too narrow.