I have a 629 PowerPort 61/2" with a Warne Maxima steel base (gives the option of having backup sights on the gun if the batteries die). A Ultradot Matchdot is mounted on top in Warne Quick Detach Rings and returns to zero when remounted well. The system works well. The Ultradots adjustable "shaded filter" and extention tube are nice accessories. The only "bad" thing is the reddot ends up being mounted very high relative to the bore.
This setup was also on a 686 6" at one time before I acquired the 629.

Woody