As was stated, a right wing can put the sharp edge of the quill into the finger for those that shoot longbows and have the arrow running on the finger. with my Jo-Jan fletchers, I have them set for a fairly extreme helical. At least as far as I can get them and still keep the quill flat to the shaft, a little bit of adjustment to both top and bottom guides. With a Jo-Jan and using left wing for a right hand bow and a right wing for a left hand bow, will put a hen feather going straight down. If feather clearance is an issue, it is with Hill style longbows and minimum nock heights, I fletch with the arrow nock only tacked on and then rotate the nock, after fletching, I rotate the shaft to get the nock and arrow grain matching as well as cocking that hen feather into the corner of the shelf. With right wing for a right hand bow, no rotation is needed and the same for left wing for a left hand bow. Other than that it makes no difference. With four fletch, it makes no difference either. I have gone to mostly four fletch and can tell no difference in shooting a mixed set, some left and some right. Neither do I get that occasional feather to finger contact.