Wouter,
are you really sorry about the M20 weight!?

I think we have the answer to the question here. If you want a 20x10 uni rigged boat with spi it is hard to get below 100kg. Marstrom started at 108 kg but 15 boats later the boat weights 120 kg. Why? The parts that have been reinforced on the M20 are rudders and centerboards.
The rest of the weight increase is a mystery to me!

/håkan