If I'm correct the iF20 is a one-design class, not a formula class. I think the F18 is much more restrictive than the F16, still the most famous class existing.

I also think being to open (for example 1.04) is not good either. The formula spirit goes to waste here. With longer/shorter hulls, wider/smaller boats, ... you may have (more or less) the same rating, but certainly not the same performance during different types of weather (waves, windspeed, ...). I think you can as well sail on a handicap rating then.

Regards,
Gill