Good question RF. Guess I should have mentioned; my favorite hunting is in a freezing drizzle. Years ago, (10 yrs) I used Scotchguard on my fletching & arrow rests. It works well to repel water. My experience is such that I no longer treat my rests. I've had the same rests on my bows for years. So far never have changed a feather rest because of wear or feather distortion.
Notice also the feathers extend beyond the end of the rest. I like it & it is not a hindurance. Originally, I wanted to trim the feathers off but did not. These feathers are longer on top. There are shorter fuzzier feathers underneath. No problems. Guess you could trim w/o effect however.
One last thing. I place the feathers in such a way as to create a semi-groove for the arrow to slide through. The net result is a very slightly raised rest of properly arranged feathers grooved for speed & quiet. It works.