Thank you very much for your message. I have a loose-footed main, a modified Hobie 18 downhaul, and a 2:1 internal outhaul. The modifications have been introduced so that the boat can still be brought back to class legal by simply using the original hobie 16 main instead of the custom-made main (tri-radial premium pentex with square top).
The mast rotation arm is intended to go above the boom, very much like in the hobie 18. The mast rotation control kit consists of a hollow cylindrical strut, two compression plates (with rivets), a bolt, a nut, and the rotation arm. So, this is my plan unless otherwise warned against it:
Drill two holes on each side of the mast equidistant on the horizontal plane from the sail track. The diameter of these holes will be equal to the outer diameter of the cylindrical strut.
Insert the strut through the mast holes. The distance between the holes when looking at a cross section will be such that the strut will protude from the outer surface of the mast about 3 mm on each sides (which about the thickness of the compression plates).
Rivet the compression plates. The idea is that the two protuding ends of the strut will now be flush against the visible surface of the plates (the non-visible surface of the plates is the one against the mast).
Insert the bolt through the strut and attach the rotation arm with the nut.
Thank you very much for all your comments and feedback,