I mounted a Trijicon RMR on my Merkel. You will need the optional "custom mount for 14mm ribs" as it is referred to by Trijicon. I did not have the removable plate on my present 9.3x74R Merkel's rib so I had to machine a 60 degree v slot on either side of the rib and a tiny locating slot on top of the rib. My other .470 Merkel had the removable plate and the plate already had the 60 degree grooves machined into either side. The Trijicon mount comes with a little roll pin and a hole drilled in the bottom of the mount where one can tap the roll pin into it with a tap hammer such that it becomes a locating pin. The locating pin should fit into the socket of the head of the forward hex head screw that is used to fasten the rib plate into the rib. The locating pin helps to ensure the RMR is placed on the rib in the same position should one decide to take it off and then remount it. I no longer have that .470 Merkel but I remember it well.

The Trijicon sits nice and low on the rib and aligns very nicely with one's eye. It can be mounted on a picatinney rail etc with various mounts available from Trijicon, but on a double, these alternate mounting methods render the sight too high for quick and utterly natural sight acquisition.

Postman.