it fits there very tight, need shorten the screw length and the base of the ring part to make the rear peep sight height as low as possible, just need a fill and 5 minutes, easy job
after install it is really solid no movement at all but still put a little AB glue to secure
the peep sight is not on the end of the barrel, but this old girl (made in Japan) lockup very tight, should be alright the ring size fits the purpose perfectly, just like some "combat" sight on rifles, the sight picture is big and still provide good reference for aiming
I have done the same to mine. Bought the same front sight but its too low. The gun is a Boito and has a high comb so I cant get my face low enough. So I bought another front sight, a higher one that clamps to the barrel then make a higher rear to suit. May go for a Lyman tang sight like on my old Winchester Low wall. I can do that as there is no lever on the tang. The trigger guard moves back. I also bought the reamers etc and threaded it for chokes. Yours has a lower comb on the stock than mine. An advantage.