feather vanes
 

Well, after tearing up 3 of my 5 good arrows I bought some a dozen bare shaft SuperSlams. I am sticking with the alums for now based on my personal testing of them vs. carbons, which was fairly basic - shoot both a whole bunch of times and see which ones grouped/flew better. Kind of not on an even field, though, as I'm using a whisker biscuit for alums. I would guess the carbons would group better with a biscuit for carbons. I fletched 8 of them with 4" red hen feathers and a black cock feather, 2 of them with 4" orange hens and green cock, and 2 with 4" plastic vanes, all with a right helical. I fletched the 2 with plastic so I could compare them to the feathers. I haven't used feathers before and it seems the feathers are flying a tad faster than the plastic. About an inch or more higher at 20yds. Also, the plastic helicals seem to hit about that much higher compared to the straight plastic vanes. At least thats what my not-so-scientific testing has told me so far. The feathers seem to be holding up pretty well going through the biscuit.

RE: feather vanes
 

Feathers are lighter and therefore, faster as well. A buddy of mine shoots feathers through a whisker biscuit, and has shot the same arrows for over a year now with no real damage to the feather.

RE: feather vanes
 

Reportedly, feathers are generally faster out to about 35 to 40 yards as they are lighter in weight. However, beyond the distance vanes are supposed to pass them as they have less drag.

RE: feather vanes
 

The feathers aren't being slowed down by drag as much as the vanes are while going through the bisquit. That might be one reason they're shooting higher, but I doubt it.

I think the probable reason might be your nockset is off just a smidge and the vanes are being deflected downward slightly as they go through the rest. Might try tweaking your nock height to see if you can get the vanes to group with the feathers. At 20 yards, they really should group together.