Back in September '02 Roger Conrad posted a photo with a thread query about fairleads on his deck and whether they were for a jib downhaul. It doesn't look like this was ever taken up by anybody.
My Ballinger rig is tuned to my Jotz racing sails. But when I use my Haarstick cruising / practice sails, the jibluff needs tightening. Currently, I thread a 1/4" line from one of the forward spinnaker cleats through a small block in the forestay eye, through the tack grommet and tie off at the stay eye. This 2:1system doesn't seem to have enough purchase to straighten the luff to satisfaction.
Does anyone have a jib downhaul system / technique that really works?