Got a spare set of unused 15.5 X-Twins in the For Sale section. US box.
I've been trying out the 15.5's and 16.5's and wouldn't recommend the 15.5's for heavier guys or bigger sails. Think about 75kg with 5.0, or heavier with 4.7. But then I think most people are riding their twin fin wave boards underfinned....
Personally I'm a little disappointed with the amount of reds I got. Normally it would be full by now, I guess it is dinner time now though. Maybe after dinner the little ones will be allowed back on the computer.
No haven't tried it as a twin. Played around with the positions of the quad set up. Found the sweet spot and left it pretty much. Quads are currently ticking all the boxes for me as far as the balance between drive and looseness goes. Would like to try some different fins but availability seems to be an issue on the eastcoast.