Those modifications were my doing.
What do you do about the Enter key on the numeric keypad? The F has a stabilizer wire which the M lacks, so if you put the black key on as-is it sits limply and doesn't click properly.
Use one of the stabilizer plugs on the lower barrel (gray, plugs in one of the barrels). It'll work just fine.
Similarly, the spacebar stabilizer wire is different - how do you get the black spacebar to attach properly?
One of the stabilizer wires will attach to the M13 spacebar and the keyboard itself.
I see that whoever did that mod changed the F to ANSI layout. I kept mine as ISO but that meant I had to stay with a few non-black keys.
That's also my doing. Unlike the M, changing keys requires less toolwork; you only need a flat-tip screwdriver, pliers, and careful attention as the plate cover slides right out.
The only word of caution that I have is that fixing broken traces is a PITA.