I installed an M7 strut brace yesterday and am unsure if I have any mushrooming or not. Most of the tower seems flat, but if I put a staight edge from front to back, it seems like the rear inside drops off about 1mm or so. I used calipers to check each side, and all the comparisons of bolt distances were the same. I installed and the plate is tight against the tower all around. Think it's OK? Your experience? Thanks! By the way the brace does look pretty cool in there!

 

Sounds pretty good to me, I have the same brace, my left side was about 5-6 mm from sitting flush, I actually could only grab two of the three studs at the same time. I would recommend looking into some of the BMW M3 strut brace mounting nuts that are sleeved so that they grab a few more of the threads on the upper strut brackets, though the standard nuts are really fine.

EDIT: Added URL for M3 nuts part number (thanks to whomever it was that first posted this on NAM)

http://www.realoem.com/bmw/showparts...=51&fg=70&hl=7

 

It sounds like the fit is fine. If you had mushrooming, you would defintely know it. Be sure to periodically check for strut mount failure, however. The re-inforcement plates do nothing to prevent failure of the strut mount.