My nacra 6.0 also needed the mast at 90' to raise. on the nacra there is a bolt through the mast and I drilled a hole in the end of the gin pole and fitted it over the bolt. Then to stop the mast rotating I cleated the mast rotator.
This will be different than your boat since you don't have the positive rotator system that the nacra 6.0 does, however I have also seen people use a U shaped piece of pipe on the end of the gin pole as well. You may still need to stop the mast from rotating..not sure..