I love my '11 Quad74 on the wave but, for my sailing style, I find it a bit of a handful to control in overpowered, rough conditions. After a good dozen or more sessions on it i still find it quite unpredictable when maxed. I really get the feeling that 13cm is just not enough fin length in the water to hold it all together with any sort of finesse.
Running the 15cm twin fins did seem to improve control a bit but the twin set that came with the board are crap and the drag just did my head in so i gave up on them pretty quickly. I am planning to get either a good set of twins or a quad set with little thrusters and longer rears to try and bring me more control. I think it will be worth the experiment.
Twice now in the last few months I have switched back to my old 08 Acid74 when things have got truly mental. A single fin has got infinitely more precision and control in the roughness.
But carving the quad is without parallel, even in onshore crap. I am a total addict for the drive you get when you push a rail. For that alone i own a quad.
At the end of the day it is a style thing. I tend towards hardcore freeride and waves. It is quite likely that a freestyle sailor would find the quad's ride quite different.
So what would i choose? The gorge is unique and without sailing it its hard to say but i think that i'd probably go with the quad, rig small, learn to deal with its character when its nuking and carve it like a mofo. On the coast there is no question.
Any chance you could try one?