Never had a pair of the M950 brakes, but very similar from the pictures I looked at. Very small head on the bolt to clear the linkage, and also a very small washer that is easy to loose. The little shoulder is the important part on the M750 though. The shoulder locates the arm as it doesn't really fit snug on the brake post the way most brakes do.
I lost some of the bolts for a pair and improvised as they were slightly beat up. I wound up cutting countersunk holes into all the arms to use standard metric countersunk hardware. If you wanted to do something crazy like that I can confirm there is enough material to remove. I had no trouble getting the bolts to sit flush.
