I have to say, that this is one tough puppy. I have been at them since the release of F1 and I just recently got 4x9 and I will probably go 2 or 3 more weeks until I move up to 4x12. I have noticed that my neck sticks out a lot in some reps so that's something I need to think about.
But, it's still a fun movement. Difficult for sure, but still fun.