I have a Center/Mark Tulle de Chase in a .62 caliber. I made a sight that is removable and mounts with the tang screw. :hmm:
I used a serpent rifle rear sight. After sight-in adjustments, then drill a hole in the box area (see below), in front of the sight plate, to accept the diamiter of the tang screw. I bought an extra tang screw and dressed it to the proper fit. I only use it to mount the sight.
To set up the sight, mount it to smoothy with duck tape, or whatever, with the serpent head toward the gun butt and mark and notice the location with a sharp lead pencil. Shoot and adjust the location until you have elevation located. Mark the box area to drill the hole centered for tang screw.
Now, mount the sight with tang screw. Reshoot marking the location of the serpants head/nose tip intil you're zeroed. Then use a sharp pointed scribe and tap a dotted mark into the serpents nosetip location for your windage center.
Now you can take it off for competitions that don't allow the rear sight. :hmm: And, then, when you want it there, put it on and line up the nose & dot and tighten the tang screw. This should be a good center, mine is. I have a small leather pouch where I keep the sight and screw when I have it off the gun. :winking:
Now, shoot.....a lot....and some more.....PRACTICE!!!!