I have slowly worked my way back to shooting 2" groups @ 23 yards from a 16' treestand. When I started earlier this year, I had a new release that really screwed me up and I could not hit the broadside of a barn with any comfort. Since I had gotten fairly good out of the stand, I figured it was time to start with the broadheads. I am going to use the Crossfires this year, due or die.
What are the causes of plaining? I ask as my first 6 shots are 6" os so high. All are centered and tight but high.
Any help would be appreciated.

Are you sure they are the same weight? I've had discrepancies of 5 gr. compared to what they were supposed to weigh.

If they are consistantly hitting the same spot your first option is to adjust your sight and only shoot broadheads until season. That surprises me that the crossfires are that far off though. Aren't they supposed to be in the "shoot like a field tip" catagory?

Your second option is to check your tuning. Either paper, French or Easton's guide.

Chances are, your nock point is a bit low. I doubt weight differences are the problem. Most would never notice a 10 grain difference at 23 yards out of the average setup.