I dont know how the I20 masts were built, but Marstrøm masts are built with pre-pregs in autoclaves. If the I20 carbon masts were done with wet layup and different fibers/cloth, you can get both the toughness and light weight if Marstrøm was to build them with his methods. I dont know the design parameters for the M20 mast, but it was probably not designed for toughness.

His deal with the Tornado class was that he was the sole manufacturer for two years (I think it was two years), then anybody could license the design and get moulds.