Axel asked in a swedish forum as follow. We did not find anything illegal, but as i told him, there are a chance it is anyway. I promised him to take the question to TC.
Can he build the floor with a curve around the plank? He will use the 1/2″ up and down from zero line so the plank gets a slot under the hull. On the upper side of the floor will make a bump for the sailor, but he is ok with that.