Had this conversation ages ago one night at the sailing club. I had a sailing mate who worked to Lola (race cars in case you did not know). His comments were that given a big budget you could get down to somewhere around 80 kg. It was really down to cost. Buy the best stuff, cook it properly and you get strong and light. BUT it will cost loads ! How much does a race car cost to build - Lots. Mucho expensive carbon !

He did a fag-packet spec, and he was saying that the problems would be the fittings. We got top the point where we were building custom carbon blocks, carbon eyes for the tramp etc. Got silly, but he suggested 80kg was possible, but expensive !