Rolf,
I didnt take your question as being on the offensive, I just wasnt clear what you were asking.

Wouter,

My foam/carbon/epoxy hulls with no bulkheads or transoms came it at 6kg per half, right out of the mold and 33kg for the whole platform, no paint no tramp. I didnt document the hull weight pre "beamed-up"

The XJ Acat hulls are between 18.2 and 18.9kgs (3 boat sample)per hull.

So if you could build a set of Acat ply hulls for under 19kg you'd be in the right ballpark and could get in under 75kg if you were careful about everything else.

Bill