Hans,
you are correct. I think the situation will sort itself out.

The Viper will win all the major events because its a better design, then the sales will follow and hence the Viper will be the default F16 boat and the rule will just have this funny little thing in it where the class min weight is 20kg lighter than the boat the bulk of the fleet are sailing. That should ensure stability in the class..

I would like to know why people are ok with a F16 that is 20kg over min weight? if an F18 was 20kg over weight customers would be screaming!