No drilling SI GSR. This is a very solid mount. If you do not want to machine your slide, this should be your only option. If you want a picatinny rail. I say the only option because it is also attached to the rear plate of your slide and it is very secure. I know that from experience you will not lose zero with this.
However, if you don't specifically want a picatinny rail which allows you to detach red dot sights whenever you want you should go for the SI G-Surfv2.
This also is a solid mount. This one is for a permanent install and you will not be able to remove your optic without losing zero. Personally, I really like this option. A little higher than machining your slide. Both of the strike industries products have the optional charging handle.
If you don't mind machining your slide and sending it away for over a month while it gets machined and painted, then these next options are for you.
The picatinny rail is universal itself. All you need is your optic to have a picatinny rail mount and you will be able to detach it whenever you want. The other option will be an RMR cut. You can get other cuts specifically for your optic, but an RMR cut is universal. Like the Glock MOS cut. They are adapter plates that will allow you to install different types of optics to an RMR cut. There are not very many adapter plates to install to other types of cuts.
