Cheshire cat,
Have you actually read the F16 rules ?
They are the least restrictive of all catamaran classes expect the A-class, C-class and 18HT class.
The Stealth R version was and is a foundation boat of the Formula 16 class and is dispensated for participating in official F16 class races indefinately. There was no need to switch from the R version to the F16 version because of the F16 rules. However, there are currently no R versions anymore as all owners decided to upgrade to F16 standard because that was easy to do and made the boats significantly faster.
Additionally, the F16 class rules also rule on the "open F16 class" were exactly the same thing that the F104 is doing now is regulated. This time on the rating 101 of the F18 under SCHRS. This area of the F16 class rules was never used much as FX-one, I-17, Spitfire and others sailors never took much interest in it. The single exception being last years F16 Global Challenge and single Spitfire crew (who I think should have been allowed to race).
Look what happened with iF20 ruling out other 20ft cats
I don't really think that that is a fair statement. The Hobie Fox, Swell Storm, US I-20 and Eagle cats were never ruled out of the iF20. Their designers and companies decided to modify these boats from the originals in such a way that they became none-compliant. The Hobie Fox remained compliant but was just not competitive enough in comparison to the Inter-20's and Hobie failed to promote that particular design strongly enough. All attention was diverted to the Tiger.
Wouter