Mark,
Have you sailed a Nacra 17 personally? Everyone I've talked to that has loves how the boat sails. SO your comments that it is "half baked" continue to be unwarranted.
I'm not saying there aren't things that can't be sorted out. But realistically these injuries are also a result of pushing the boats hard (double trapping downwind isn't easy either) in tight quarter big breeze racing. We've had F18 events in big breeze where people have gotten hurt. The speed these boats go and how fast they handle make everything much more dynamic and more room for error.
There are multiple reports of gusts to 40. It is the Nacra 17 class's job to prevent these survival scenarios at major events, so far not much has been done obviously.

Also there is no "n" in 49er.