The minimum weight for the F18 large sail plan is 330 lbs, so anything over that may not work in your favor in moderate and light conditions. I've never sailed the I20, but raced a H20 for many years. While it would over power quickly, it was more forgiving for heavier crews.

Me and my regular crew are about 155 lbs, so I spent a lot of time depowering to get it flat.

I think another thing to consider is how active these fleets are in your area. That is the initial reason I switched from the H20 to the F18 3 years ago. Even though I still race with my daughter some on a H16, I love that spinnaker.

If I were buying a boat now, I would definitely consider the Blade 16. But that decision would be based mainly due to Loyd's and my weight and the versatility to race without the spin with my daughter.