I just mounted a new Marbles tang sight on my .45-70 Miroku Model 86-EL via using the longer tang screw only.
It fit right over & hid the tang safety, which I pinned in the "off" position.
Since the top tang's surface is slightly convex, and the Marble base's underside slightly concave, they mated tightly and never shifted zero through 5 years of hunting with it that way. I DID check the tang screw for tightness prior to every outing, though.
BTW - I also switched out the rear barrel sight for a Marble's folder, which allowed me a short-range (75yds) zero for the bbl sights, and a longer range (150yds) zero for the tang sight.
YMMV, on the zero distances desired.
.
