I always wondered how a hully midlength would surf if set up for 2 hi-aspect semi-flex fins out at the rail. You'd probably have to use a somewhat stiffer fin than you'd use in a singlefin. Maybe less cant than a thruster set. Like a Zinger or a Twinzer without the canard or the concaves. The board would still drive off the rail line and not the fin cluster and you wouldn't need a really deep fin for it to hold - maybe 6" or so.
OTOH, ACE (who was one of the shapers for the Zinger) favored a wierd low-aspect potato shaped fin for those boards (not a regular fin shape as shown below). Kind of like a keel but with no tip, but those boards had the canard and the heavy bonzer bottoms. Still, what he was doing was closer to a fish-style keel.
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Love these fin set ups. 7'6" and an 8'er. Tried other fin set ups and so far these two are the money ones for these particular boards. The large flex twins great in up to overhead. Super loose but still with great drive. The other twins with the bonzers are flexy and good for well overhead.
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