I run 1" nylon webbing
from the stern cleat to the bow cleat. Yes, it would be difficult to get back on if I was at the end of my jackline, but the cleats were there, and all I did was buy heavy duty nylon webbing online. Cheap and easy.
The downhaul is easy. Block at the stem, bow cleat, whatever, then run a line up to 8-10' from the head. Done. I tried it on my boat, but it didn't work too well with the tuff luff.