Pete, I'm sure the boat designers could give you a ballpark "design envelope" windspeed which would be helpful if you had to pick an arbitrary windspeed as your "no-go" point.

I suspect the N20 is around 20 knots (sustained), the F18 and F16 maybe 23-24?
Can you sail successfully in higher than design limits? Sure.

Should you? Possibly (depending on other factors - crew, course, support fleet, etc).

Beyond design conditions, it would be expected that the fleet would suffer greater chance of equipment breakdown, possibly endangering crews and officials. It is at this point that the PRO should step in and weigh the potential risk vs. the safety/support capability available.

And to echo prior posts, the guidelines the PRO will be using for determining when to race should be made available in advance to all participants