Greetings,
Thanks to Wouter for jumping into the fray on my behalf. I'd just like to add a few thoughts of my own:
1. I got into this with my eyes wide open. I chose the Nacra 5.0 because it fit into the basic box limits of the F16 class and I could pick one up REALLY cheap. I was aware of the weight and non-board limitations of the 5.0 when I started.
2. I also happened to have my last set of sails from my old Cobra gathering dust in my garage. I found out these could be cut to fit the optimized size for the F16 class for a small investment. Since I happen to live in So. Cal. Skip Elliott, who made all the US Nacra sails, is doing the work for me. I'm also talking to him about a gennaker. I'm pretty sure at least my rig will be up to the task.
3. All of that meant I could put an F16 together and get on the water in a short time for a reasonable cost. My logic was and is, if I race in the F16 class 2 or 3 times a year, who cares how fast my boat is? And if I find myself racing more than that? I can build a set of lightweight hulls to fit the hardware off my Nacra and will get a close to optimized F16 without a huge initial investment.
4. As for "getting close" - if I remember right, that's why we race the races. Slower boats, cars, horses, etc. (Do women fit in here somewhere?) have been scoring wins for years. Personally, over the years I won a few races with a much slower boat and lost a few with a much faster boat. I still believe the "nut on the tiller" makes the most difference.
And as Eric Poulson, the F16 West Coast rep who sailed a Nacra 5.0, suggested, the limitations of my Nacra F16 will be less important when the wind comes up.
The verdict: even though I didn't know the F16 class existed until early May, I should be racing one a got with pocket cash by the last week of June. And that's pretty neat - and a lot more fun than looking at pictures.

Good sailing to all.
John
Nacra f16 (USA74)