What if you....
This is something I came up with when I had a similar problem and closely examined the tumbler.
It would also make stealing a benz with this type of ingition a snap, but here goes, feedback will be appreciated.
The tumbler is basically two tubular pieces of metal one inside the other, with a metal cap on top, where you put the key in.
In order to remove the tumbler, you have to turn the cap to position one so that the two holes in it align with the pins.
In reality, or at least in my car, both the old and new tumbler had only ONE locking pin, on top of the tumbler, the bottom was blank and posed no problems when removing the tumbler.
What if you simply take a drill of some similar size to what the hole to the pin is and drill right through the metal cap. Of course, you would have to have the drill aligned with the hole to the pin but this should not be that big a deal. Once you drill through it, simply stick in the recommended wire and remove the tumbler with pliers or something similar.
I have not tested this, but this is again why I'm asking for feedback.
The entire process if done right should not take more then 5 minutes, and I think it would be a much better alternative to griding down half the tumbler to get it out.
1985 190E 2.3L - a constant project.