I don't. I use my spine tester to find the stiffest side on all my arrows before fletching them. Put the cock feather right on top of the stiffest portion of each arrow.

You're doing the same thing I'm doing, just a different way of getting there. Extra steps you really didn't have to worry about with aluminum.

Isn't it amazing though how far we've progressed! Back in the days of wood arrows, we had to use spine testers to get a matched set of shafts and were constantly checking them for cracks while we were shooting. And now... uh... HEY! We're back where we started from!