I got a pair of K4 Rockets (17.5) to run on my Goya Custom Quad 106 in twin mode - gave them a first real try out yesterday at Cott with a 5.5m sail comfortably powered, hardly any swell - pretty much the conditions I got these fins for.

These fins do exactly what they are marketed for - they are quick to plane, fast and they tank upwind. All of these are features of the Goya Quad anyway but definitely more so with the Rockets on. The Goya still felt loose enough in twin mode to mess around on the very small waves on the day.

I have to say though that the plastic is verrry soft. The trailing edge tips are bent over just from sitting in the board bag with fins on. Time will tell but I have concerns about the longevity of these fins. They are of course cheap so you could afford to replace them more often.