I think helical fletching is a good idea, especially with fixed blade broadheads and shooting off the shelf. I'm also using 5" feathers, could probably get away with 4" but I'm not shooting far enough for it to matter and I'd rather have a little more forgiveness.
Shot today, first time in a week with the rain. Shot pretty good, used my broadhead target, its black and I noticed a little erratic flight with the white fletchings. So I tried a bareshaft, hadn't in quite a while, since I first tuned. I was getting a consistent slight nock left flight, every shot was the same. Which means my form is consistent now that I am used to the bow(could also be my draw length got a little longer as I've heard can happen at a heavier weight when you get used to it), but the arrows are still slightly weak, need to cut them a little more. I can take off at least another inch, shouldn't take that much, maybe 1/4 or 1/2". Should make the bow more forgiving and stop some of the left/right misses. Back to the arrow saw.