A very interesting discussion, I'm just a dreamer but feel I've learnt a bit just following this and the prior thread, thanks to all that have contributed so far.
Seems like displacement can make all the difference to performance, but it also seems to be one of the least trustworthy numbers. Last two boats mentioned range from 5.5 t for a 46', to 16 t for a 52'. Assuming the 5.5 t is right, and cubic scaling, then you'd expect ~8t for the 52', caeteris paribus. Of course there are many other variables, but how much trust can be put in an advertisement? Do buyers routinely check, if so how