hi Sebastian,
great to hear of someone else giving an old cat a new lease of life
my hours searching for nacra 5.2 info show this forum to be the place to come to with questions

for 5.2 pics you might want to visit airborne's collection and compare them to your boat
http://good-times.webshots.com/album/558964894sVJNBainfo

the above pdf manual is good but it is for later model boats with the adjustable spreaders etc. i have an earlier 5.2 manuals which i will start scanning

the standard halyard is used to pull the sail to the top of the mast. it is then pulled forward until the ball on the cable can be locked under the tang at the top of the mast. if the mast isn't pointing into the wind this can be a little tricky. also you have to hook onto the ball and not the rectangular blob which is a few centimeters below the ball
once the main is locked in the base of the sail is pulled down with the downhaul. my and airborne's use the oem system with very little purchase. a double pulley on the hook and a single pulley on the mast base, (but as they are now you can only use 1 of the pulleys on the hook). the rope is then cleated off. a simple upgrade would be to replace the small block on the mast base with a double block so that the 2nd pulley on the hook could be used, have tried to attach a composite pic showing my and airborne's downhaul system, gree is experimenting with a more modern system

eric e