Easiest way to 'fix' an A2 stock install on an MP-10:
[A2 Stock Issue
It will function AS-WAS if you make an aluminum (or whatever) cylinder to drop down the longer A2 tube, then just drop the stock spring and buffer on top of it. If you will carefully measure the inside length of the stock S&W folder's tube, then the inside of the A2's tube you can determine the length of the plug(cylinder) you need. This will trick the stock parts into believing they are still in the stock S&W folder.
I have heard that a stack of quarters will suffice in the interim. Cheers!

Yes, it works and not a hiccup..