I've got a King-Kut system on my New Holland head, been on there for the last 2 seasons.  It's been fine, I might have replaced one guard, I've been through a few more sections, but that was more my fault.  The only problem that I've had is because of the overlap in the middle of my dual drive head (larger New Holland heads have the option of a dual drive head with a shorter knife and a gear box on each end).  The overlapped section was causing problems when it would get bounced up and catch the end of the top piece, then bend it and the end section up about 2 inches, right in the middle of the head.  I seem to have solved it by adding a hold down closer to the middle.

Anyway, I've been very happy with the system and the holddowns only take a little adjusting every once in a while.   It's a lot better than the systems that you adjust by trying to bend a hold down with a hammer and bar (like the Case factory setup for 1020 heads).  I know 2 other guys running the Crary on Case heads and they are happy (one of them convinced me to go this route after his first year running it).

Mike