Hello Patrik,
If I were you, I would not attempt the project. A 5% mast section: the max thickness is 5% of the chord. This means if the mast is 20cm on the chord measurement, it is 1cm thick at max thickness. This is way too much difference in fore and aft stiffness and sideways stiffness. For 27sq meters of sail area, this mast would be about 40ft or 12 meters tall. A 12 meter mast that is 1cm thick at max thickness will not stand even if it were solid carbon.
I think you should forget this project.
Bill