In my humble opinon: Run (don't walk) down to your Hobie Cat dealer and put one-of-these on your cat!
I went crewing on my friends 16 two weeks ago (F4-5, 11-21 Knots wind speed) and he had just installed a 6:1 downhaul. This is the " True Turbocharger" on a Hobie!!
I could not belive what a differance it made in the speed and controllabilty of his cat, in rough and calm conditions, jib trim; et al.
I would love to find-out how this reacts with a "Flathead" sail, but now I know why I want one.
Ya, I'm a Rookie. But I learnt' something...
Hit the books: Catamaran Sailing, Phil Berman, Hobie University, NAHCA (Performance Sailing Quiz), or anything that you might have, and see why this thing works, and learn how to use it. It is good.
I just own a H14T but, PLEASE support your Hobie Cat Dealer!!!! Keep the parts supply, and the Company alive for all of US... Mel, at Inland Sailing, in Sacramento, Ca. is a GREAT GUY and has helped me alot!!