I've been on a speed chasing mission a bit myself. I can consistently hit 21-23 knots in 10-15 knots of wind. For the record, I have fast gear, Mikeslab and a variety of wings designed to go fast. All this said, I've capped out around 25 knots for max speed. Where I wing most often, the water gets too rough when the wind is blowing hard enough to get past the 25 knot mark for me to be able to push things harder.
I would strongly suggest watching some of this guys videos
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He's covering most of what aligns with my experience. I will say, the PPC M1R definitely goes faster than most other wings by 1-3 knots. It's also so stable at the top end that I can cruise at higher speeds as well.
No matter what the gear, my experience is that there is definitely a skill factor that starts to come into play to get past 24 knots then again at 25. I haven't figured out the + 25 thing yet, but I'm guessing it also involves going to a very flat spot with solid wind.