I have installed a Meprolight Tru Dot front night sight onto my 4" Ruger GP100 (with a little fitting), but the rear sight will not seat correctly. I noticed that on the bottom of the stock Ruger GP100 rear sight, it looks like the bottom sides of the sight are milled narrower down the middle, but the Tru Dot sight is totally flat on the bottom. The rear Tru-Dot sight will install, but it won't adjust down at-all. I have emailed Meprolight, with no response. My Ruger GP100 was made in 2011.