For anyone who is curious about how a twin fin (or at least mine) feels to ride:
I've only had a couple of actual side-on wave sessions on my twin plus a few bump'n jump sessions with 4.7-5.6 sails. So far these are the initial impressions I'm getting from the twin:
1. The board feels a bit slower to plane than a comparable single fin, but I'm finding that this feeling is becoming less as I become more efficient at finding the board's sweet spot for early planing. The extra width and volume (57 cm and 85L) is really nice for slogging around in wind that would have me up to my eyeballs in water on a 74 L board, but it still feels balanced even fairly overpowered. You get more range out of one board.
2. Once up and planing, the twin feels pretty conventional, ie no nasty habits or tendencies. You wouldn't know you are on a twin. It sails much like an Evo in the way you sail with more front foot weight than, say, an Acid or more traditional wave shape. The board feels smoother through our local ugly chop than most wave boards I've sailed, partly due to the narrow tail. Upwind feels at least as good as my single fin boards.
3. Jumping the board feels really compact, controlled and lofty; really nice for looping! I haven't noticed the twin fins slipping on take-off like some have reported. Speed into jumps feels good as well. If you know how to sail fast, the board will run for you. If you sail it with a heavy backfoot it will feel like a dog towing a bucket in the water.
4. Jibing feels a bit more technical. The board feels less directional so it will "hunt" for a line if you aren't leading the board through a committed arc, making it initially feel squirrelly. It wants you to give clear input to come out of the turn with speed or it will stall with less lift offered by the fins around the corners.
5. Turning, banking, and slashing is what the twin is best at! The lower fin bites and more of the rail gets engaged to carve deep gouges even off of swell or chop. To me, this is the special part of the twin. I can't wait to sail it on the Oregon coast!
So is the twinny better than a single fin? Well, mostly it is just different. For my taste, the twin does everything that I enjoy doing in windsurfing (carving/slashing/looping/wave riding) in a really engaging and responsive way. This all being said, I still think the single-finned Starboard Evos (esp. the 74 and 70 L Evos) are way ahead of their time as they feel the closest to sailing a twin fin of any board I've sailed. If you don't like the feel of an Evo or sail with an especially heavy back foot, a twin fin may not suit you.
I'm betting that the twin fin design knowledge will only serve to freshen up some of the rocker lines and outlines of newer single fin designs (or trifins or quads etc, etc). It's all one big circle, but it's fun to shake up our sailing by riding new shapes as they are developed once in a while!
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