I've measured my Hobie Adventure Island sailing and pedaling speeds with hand held Garmin Gmap 76 GPS a number of times, and these are the results.
Sailing in 20 knot winds, my top sailing speed was 9.1 mph. Since outrigger and bow were submerging in waves, I think this may be about the maximum speed I can attain without modifications to reduce plowing under waves.
Pedaling in flat water, my top speed was 6.7 mph. I could cruise comfortably in the 4.5 to 5.5 mph range. Pedaling was done without outriggers, sail, dagger.
I also did a 15 mile pedal on a 90 degree day a lot easier than any similar distance paddles in my former racing kayak, a 40 pound 19' x 19'' kevlar kayak. This surprised me because the HAI hull is 65 pounds, only 16', and wide. Legs surely are much stronger and efficient than arms/torso.
What speeds have you achieved?