I can't see it Wouter. If it is so great to be part of F16, why didn't Cirrus build an F16? No, instead they built a boat that's close enough to be ALLOWED to sail with F16s. If there were no 'grandfather' rule that allowed NEW boats to 'measure' in, Cirrus would have had to decide whether F16 was attractive enough for them to build to the box rule.
As it is, a purchaser of an Evolution can now hedge their bets by purchasing from a builder with a proven track record, sail 'Open F16' or OD if it takes off. If this option weren't available that purchaser might have gone and bought a Blade, or a Stealth, or something else completely.

I don't see how it does us any good at all to say "OK, you can play with us" and then turn round and say "Oh, you're too quick, you keep winning, we don't want to play with you anymore". If we've got a set of rules that are in the public domain, and someone wants to build or buy a boat to sail F16 then IT SHOULD MEASURE to the Class rules.

ONLY existing designs at the time of the adoption of the rules should be elegible for 'grandfather' status.

Just my 2 pence worth.........

PS. What's this in the corner of the Evolution pic? :