I am buying a Glock 19 and a 27. Both guns have the default fixed sights, but I want adjustable sights installed. The guns have not yet arrived. The photo shows the sights I want to install. Any comments on this sight? Will the frame of this sight allow it to be (gently and carefully) tapped into the Glock slide, or is this a press in installation only? I have never owned a Glock but I am assuming that the fixed sights will need adjustment, so I would rather add adjustable sights now.