At las I ended middle of the road, and got a 5'5 wave. much lighter than my higher wind legacy and zetas, but more supported having 4 battens (It has that nice Ezzy Belly)
Just 4 days ago, I was foiling with a friend who rigged both a HS 6.7 and a Fringe 5.5. He preferred the Fringe.
I have neither since I foil with old Sailworks sails, so I can't comment from first hand experience.
I can't comment on the Fringe as I've never ridden one, but I have ridden the original Hydra (Similar to the Hydra Pro) 5.5 and I greatly prefer it to regular non-foiling specific sails that I've foiled in the same size. I have found the "canard" wingtip under the boom gives me a bit more balanced backhand pressure and really helps in lightwind when I'm "paddling" the sail and pumping the foil through holes. I am a strong believer in the short battens, at least not on huge sails, I haven't tried anything bigger than the 5.5 , but I really love the depower it offers in higher winds. I haven't experienced any difference in getting upwind vs. a standard windsurf sail.
I'm all the opposite. The fact that I max my outhaul and mid to max my downhaul, i can pump much faster and generate more power...as soon as I'm up, it seems to be faster and do better in lulls. But I'm using slow foil, pryde medium.
No worries - happens to the best of us I've been trimming my Hydra Pro 8,5 on minimum in light winds, but I don't get the power I need from pumping. Also the backwind is killing me in the gybes. Next time I will give it a go with max DH and 150% long chord on the outhaul. Tnx for the tip