I installed DPM guards on my CB1000R when I got it new.
The job was tricky, cuz the rear hole in the engine casing needs to be drilled to correct diameter, then tapped (it's just a 'blank' hole as it comes from the factory). I did this by hand, and drilled the hole on one side slightly misaligned - angled forward a bit. Then of course, I needed to open the 'pocket' in the engine guard out quite a lot, otherwise the head of the bolt wouldn't seat because of interference with the guard.
Last autumn I low-sided the bike on some gravel. The guard did its job, and despite taking quite a grinding, preserved the 'vital bits' on the bike so that I was able to just basically dust it off and ride away.
Now I'm ready to replace the part. Originally I just used the side of the 27/64" HSS bit to 'mill' the alu back, to the point at which the bolt seated properly, but this was a slow, cumbersome process - the hole needs to be elongated about 5mm, and you can't drill out the 'plate' at the bottom, so there's a lot of dicking around.
The alu has to be removed back to roughly the yellow line.
Any suggestions, other than repeating my earlier process?