there is a rather easy way to set up a convenient back up system, i have been forced to do that two times.
Mount a block at the connection where the boom and mast meets. Take a line to the block at the back end of the bom and attache it to the sail, the other end you take to a block at the rail and lead it back to the cockpit, see attached photos, Maybe you do not like the way I attached the block at the boom base, the pictures are from my first attempt I have tried different ways, you can experiment what you find suits you, I use soft chakle .
the set up work very well.
Paul on SY Kerpa SM 259 in Horta