Having been one who has pushed my F31R very hard and to the limits (but not beyond) I can say that it is very stable, so much that I race with my wife, and two kids who are now 8 and 11. They have been sailing/racing since they were 3 wk old, either on a F27 or the F31R.

We have reached a max GPS speed of 29kt during a race, but that probably included a 4-5 kt current, at the same time a Firebird capsized while crossing the starting line. I have launched the boat off a wave completely heading out to Block Island, I have stuffed the bows to the point that water was past the mast and all the crew including myself thought we were doomed (the boat rounded up and set back down right side up), and flown the main hull in 30+ winds with full main (not fast, but fun) in Naragansett Bay, RI. Sailed in 12-15' seas off of Gloucester, 20-30' swells around Block Island. I would never think of taking my family on a mono and pushing it as hard as I did the tri. So For stability I would say the F31R is excellent. Having had both the F27 and the F31R, the 31R, when reefed, feels very much like a F27.

The 31R1D utilizes the same shapes, but sports a larger main/jib, rudder, daggerboard, etc... It's a faster boat.

I would never think to take a F24 in winds over 20 or seas over 3-4' These conditions are extreme on this boat. Or at least the couple that I have hear of capsizing were racing at the time and pushing the boat pretty hard I imagine (we were way ahead at the time so we didn't see it happen.)