That depends on a lot of things (crew weight and knowing what to do with it, ability to handle gusts, etc.), but one thing is certain.....you will flip it eventually. You should be OK up to aboout 10 mph for now, but this brings up an important point. I've scanned through this thread, and righting the boat hasn't beeen mentioned. You need a righting system, and you need to practice with it under controlled conditions with assistance available. Search here and the Hobie 14/16 forum, and you'll get lots of ideas.

Once you've flipped it a couple of times and know you can right it, you won't be so worried about capsizing....it's just part of the game!