Atlasman,
It seems as though you' ve done your homework in trying to find the problem. Fletch and C903 have both given you good advice. Sometimes tuning is a simple process and sometimes it makes you pull your hair out.

The only other thing I can think of is that your shafts are possibly right on the borderline for spine. I' m not familiar with those shafts so I can' t speak from experience where they are concerned. I can say however, that some of the charts seem to be a bit off these days. The bows have gotten much faster which in turn demands more spine from the arrow shafts. I think some of the arrow charts are being left behind by some of the newer/faster bows.

A slightly underspined shaft can literally drive you crazy because it can paper tune and shoot field points perfectly, but the fact that it' s wobbling through the air like a wet noodle makes it go haywire with broadheads. I don' t know if this is your problem, but it would be worth looking into. You can turn your bow down a few turns and then go through the tuning process again. Make sure you' re still getting bullet holes and groups and then try your broadheads again. If this fixes your problem and you want to shoot the heavier weight, you can always go up in spine on your arrow.

I have had problems with underspined shafts in the past, but have never had any problems getting extra stiff shafts to tune. Just thought I would suggest it.

Good luck getting it shooting properly.