Fellers — you might get more response on this one over on the bow and arrow forum. I can’t help as I don’t crest. But I do have cresting tape on some arrows and now am inspired to take if off and see how much if any it affects FoC. Certainly, if changing fletching a little bit can alter FoC, 6″ of fletching tape, and perhaps a lot of fletching paint, can logically do the same.
Now, someone please remind me the best way to remove fletching tape!