Contact Heinie directly with this question. Depending on your specific pistol, it is possible to pair a Heinie front or rear sight what is already on your slide.
No. Heinie Glock sights are a “crush” dovetail fit. They do not need to be filed or altered in any way. Filing or altering the sights can cause the rear sight to fit incorrectly.
No. All Heinie sights are designed to “cover the target”. POA/POI
Any time you make after market changes to your pistol internally, it can affect the POA/POI.
Yes. Heinie always recommends shooting your pistol before removing the factory sights. Heinie sights are designed as replacement sights and do not change the POA/POI. It is important to know how your pistol is shooting with the factory sights before making any changes.