Lots of great infor here and all valid points!
I will throw my opinion into the mix.
I love 4 fletch, I find a good tuned arrow will stabilize even quicker with 4 fletch. I do try to use a smaller feather when I 4 fletch.
I have always been a big fan of 3-4” parabolic feathers as they have less drag than 3-5”, or even 4-3”. And are MUCH quieter. We have done lots of tests on sound and found that parabolic is much quieter. Even with 4 fletch.
In my typical hunting situation, I like 4-4” parabolic so I get the best and quickest stabilization at short ranges. I typically hunt 20 yards and in, so, drag is not really an issue. If I would hunt in open areas where I might take a shot at 30y, then I would play with 2”-3” 4 fletch configurations.
Last year I shot the 2” gateway Batwings for field archery and hunting. I was very impressed with these little feathers. However, lots of time and tuning needs done to shoot a feather that small.
This is why the A&A feather is a great choice. 2.5” 4 fletch is a great balance for most hunting/shooting situations. The A&A feather is pretty impressive on stabilization and drag.
One more thing, When I 3 fletch, I put a helical on the feather. When I 4 fletch, I do straight. The helical with 4 fletch manipulates the flight too much for me. You can see the arrow rotation too much. IMO