I use an MGW sight tool to do my Glock sights. The directions are specific and in bold, tell you to install the new sights from the right, pulling them into the slide from right to left. They also tell you to remove the old existing sight by pushing them out to the right.
I dont know if there is a taper there or not, but the couple I've done, I did as directed, and all was good, or at least, installation wise. Removal wasnt as pretty.
The couple that I removed, came out hard and in both cases, the original plastic sight was destroyed, leaving a little metal wedge/shim behind, that I had to knock out with a punch. Im accustomed to installing the metal sights, and understand how to "fit" them if they are tight. Im not sure how you would do that with the plastic ones, or what will happen if they are overly tight and you try to pound them in.
The sight tool is worth the money if you have a couple of guns and if you like night sights. It also works well for adjusting the rear sight for windage, and allows for more precise adjustments with no damage to the sight.