Finally got the 407k in and mounted everything up (EPS Carry OOS), however, I think I want to rid the use of a plate, did you have to shave the front at all or simply get rid of the rear posts? Dremel?
On my 3.1" Shield Plus slide I removed the rear posts. Didn't know about the plates at that time and I'm impatient, sometimes.
I did it with a small hobby belt sander. Very carefully removed the rear posts (managed to do that without messing up the finish in the slide cut and still don't know how I did that
With the back posts gone I found the 407 would still not go flush, up front, with the slide/cut. I had to remove just a very small amount of metal off the top of the front posts with that 1" wide belt desk top (yeah, Harbor Freight) belt sander to get the Holoson to sit down flush in the optics cut.
I think I've got a picture. Can't find on showing the removed, or shortened pins. I guess when I got it right I just left the Holoson on the slide.
Here's a picture showing why I had to shorten the front posts. After removing the back posts the optic sat down perfect in the back but high, with a gap in the front. I took just a few thousandths off the tops of the posts up front and fit tested till I got it right.
Very happy with how it's working for me.
A file should work, but it's slow. A dremel should work if you're very careful and have a steady and strurdy hand/grip. You know how a dremel can kick out/sideways on you sometimes. I've used that little benchtop hobby sander on several small gun projects in the last few years and just figured I'd give it a try.
The plate is quicker and easier and not too expensive (the DPP plate from Amazon). It does raise the optic up a little but I can still see the top of the front sight on the 4" slide where I did use a plate.