Federer is actually shanking less now than he was a few years ago, much less. The difference is that as of late he has been shanking forehands. We can only speculate as to why but I doubt it is because of the racquet.
I havent really looked closely at his kfactor racquet but I have noticed that kfactor 90's have a thicker beam than the tour 90's, especially so in the direction of the strings.
Donnay Gold 99.