If I recall, you stated in a previous thread that you no longer recommend bolt modding a 122-key Model F, though I forget the reason why.
Out of frustration on my first F-122, and since I had done enough M bolt-mods that they were no longer intimidating, I drilled about 8-10 holes around in places where they seemed appropriate and then cut off the tabs, since they were giving me the trouble. I used 4-40x1/2" machine screws and nuts with washers, and the results were pleasing.
Afterwards, on the 2nd try, I got my holes off a bit and they did not work properly, so I deprecated the procedure and recommend leaving the tabs in place to ensure accurate alignment of all the plates. With low-end equipment, a hole drilled in metal plate and off by 1/4 of a diameter is almost impossible to rectify.
I do, however, always add 2-3 bolts along the center of curvature of any Model F that I refurbish and I believe that it does a lot for stability, and is particularly helpful if you have replaced the foam with something firmer. I don't know whether the plates get "un-sprung" when you take them apart, but pulling them snug in the center seems to make everything much better. A couple of times, there were several keys that did not work at all until I cranked them down tight.
