Stick the pin thru the top hole and leave about 3/8" above the stock...then tighten setscrew slightly and Check the lock/unlock function. Adjust if needed.
Tighten screw with a 5/64" allen wrench. Test several times & make sure it's right where you want it.
Slap in your 795/70/995/989/989m2/etc barrelled action and it's a done deal!!
There is a little play once you are done, but it's really not any worse than the wiggle it already had.
However, I think building up the back wall will resolve the stock slop...I'm considering epoxy or some sort of plastic filler.
Heck, even a little moleskin might do the trick