I am putting a Fastfire 2 on a S&W 57...I am confused as to the weaver base needed. model 401 black or 48109 # is what Weaver told me for an N frame size, but I see on other web sites, they come in either 1 piece or 2 pieces. Am I correct? For a small sight like the FF2, would the small base work? My gun is already drilled and tapped. Do I place it above the centered above the cylinder to help keep gases off lenses? Or what is proper placement, just common sense? Thanks, Tony!