I do most of the work and training with my brother. He's starting to throw a 2-seam cutter, basically he is taking the tradition 2-seam fastball grip and overloading the right seam (he's a righty). He holds it very similar to the picture below, but not even as drastic:
Now my biggest fear was that he was supinating and throwing something similar to a slider. But I don't think that's the case at all, i think he;s just throwing it off axis and has never complained about any pain. The break is away and down, but is very tight and late. I just wanted to make sure this was ok to throw.
Also, does the cutter hinder your fastball velocity over time or is that a myth. Thanks guys.