Hi, i don't want go in a no way discussion, like we said in French "avec des si on mettrait Paris en bouteille"
I try to neither listen rumor, and speak only what i know, and what i see.
I don't believe to miracle, light, stiff, not expensive have a limit.
For have some ideas
a Viper hull is approximatly 10 kg heavyer than an A class carbone one. An F18 hull is approximatly 20 kg heavyer than a Viper one.
Now, do you feel hull are heavy ?
I could said Viper is really stiff on sailing, try it if you want ... but also a Viper is realy strong, customers have already hit a rock at important speed (spinaker and trapeze in 2-up) daggerboard are a litlle short now ;-) but hulls haven't dammaged. (don't try it) This day, he doesn't think about weight of his boat, but only broken or not ?
I could jump with my 90 kg on a Viper daggerboard without risk, i don't break it and flex is little. I couldn't made the same on my A class. Yes, my A class daggerboard isn't so heavy than my Viper one, and it's strange but my F18 daggerboard is too more heavy than the other ;-)
So a stiff boat, with stiff beams, with stiff rudders, with stiff daggerboards, with epoxy glass build for hulls, etc .... are choices.
These choices give a Viper with his weight, and his price. And a Viper is a really fast boat and not so expensive, so why change something, all are happy, the mixture give a good result.