Hello, I live in Brazil and own a Nacra 20. Sometimes I sail alone and I was wondering if there is a "system"to reef the main?! Thanks

Get a sailmaker to put second tack and clew eyes/d-rings where you want the reef, and some across the new foot so that you can tidy the sail with elastic. just like a Hobie 16 mainsail has got
Make up a wire strop the right length to add in between the headboard and the halyard shackle so that it still hooks over the lock at the masthead. You may need to capsize the boat to get it to hook up.

Don't use the spinnaker if you are reefed

Don't singlehand a 2-hander if you can't right the boat after a capsize

If you have the carbon mast,do not increase the load on the carbon luff track.

I'm puzzled by what you mean by this. How would reefing the main increase the load on the luff track...not to mention the fact that the carbon one is probably stronger than the aluminum one.

In this arrangement the maisheet load will not be on the halyard hook. But on the luff track, sheet in & the first thing will be OOPS.

Yes, if lay up was a little thicker.

One could loop a line around the mast and through the grommet in the head of the sail, to prevent pulling out of the track?

the A class cats use a carbon sleeve around the mast with a 2nd halyard shackle clip on it and a wire strop from this to the top of the mast. they cant reef on water with this system, they have a smaller heavy weather main to use it with.

get a recut main that has the top two panels cut off but still attaches to the hook.