Not quite concrete when I got her she was in a bad way, side of one hull had folded and the decks had let go. The foam had absorbed water that they never let out again. I put a series of bulkheads through with foam under the decks plus the cloth and resin. I probably added 10kg but she was always heavy which didnt worry me as I sailed her with my 10yo daughter and the extra weight settled the big rig down. That weight included everything I used on the water sails, mast etc.
regards