I've never had my racquet head "shorten" on my K-mate. I've strung on it about 100 times.
I DID have a frame get sidecrunched when I let a friend string it on his new cheap electric pull: he did what that other guy did---did not mount the frame securely in the first place. IF you don't mount the frame, this happens. Pretty dumb mistake.
To Praise, To Bless, To Preach--the Dominican Order