Was fiddling round with my heli and searching through my bag o parts and came across a 500 headbutton. I usually never run headbuttons on the 600 head because in the event of a crash they can usually do more harm that good when a blade grip smacks it, especially if its a metal blade grip($$).
Sooo, I grabbed a drill and drilled out the mounting hole on the 500 headbutton so a 3mm bolt would fit through and voila, it fits great and now the blade grips don't hit the headbutton. Yeehaw.
The bolt sticks out a little, but one could probably countersink the hole and use a countersunk bolt to get it flush. The bolt sticking out now a little doesn't bother me though and kinda helps keep the head centered while stopping it.
I'm sure someone's probably done this before, but I just ran across it by accident and figured I'd share to those who may be interested.