I had some time during a meeting, and was able to mount the optic without issue. Some notes:
The front lugs on the 04 baseplate were 1.0mm tall. The Holosun HS507K indents were 0.7mm deep. I filed the front lug down to approximately 0.6mm, using the sight as a reference, sitting it on the baseplate backward (the rear lugs were still present at this point) until there was no light visible under the lugs. At that point I measured the lugs, and they showed 0.7mm. I filed them down a few more light strokes, and they now measure at ~0.65mm.
I filed the rear lugs level with the surface of the plate. I wasn’t super careful not to mark the plate itself, so I filed until I was making contact with the plate on both side of the lugs. Once they were smooth to the touch, I cleaned up the places where I removed material with an old trigger stone, just to make sure I didn’t have any burrs sticking up still that would interfere with the mating surface. This step is probably unnecessary.
Finally, I used a black Sharpie to paint over the exposed metal. It doesn’t match and looks like shit upon inspection, but it’s “good enough” for the moment. If that bothers me over time, I’ll refinish it. I thought I had some Birchwood Casey “Aluminum Black”, but can’t find it at the moment. I’ll go ahead and order some more, and if the mismatch bothers me I’ll tear it back down, strip the paint, and hit it with that. Matte black spray paint would almost certainly work just fine as well as long as it was applied lightly and evenly.
I’ll attach in-progress images from my phone in just a moment.