The jack line is just to guide the hanks and it should be installed by the sail maker as required. It should not be something you need to adjust. I never have seen the need.
Getting the sail through the slot is mostly something you get used to with timing. The good news is it really is the same timing you would do on any jib. With a sloop
you can get away with a sloppy tack. When you back wind
it properly and it will go. Being lucky still counts. I did install a tacking line on my last boat. What it is is a line the size of a furling
line run though furling
blocks next to the real furling blocks. I then attached a down haul of fixed length as far forward but aft of the furling hardware
to an eye I had on the bow roller. I adjust the down haul so it puts the block as far forward with a fair lead to the clew. The tacking line goes through the block to the clew of the jib. When the knots of the sheets
on the jib hang up on the inner forestay you can pull the tacking line to make the clew go forward and down thus becoming unstuck so the wind
carries it through. This is not a free lunch however in that it becomes another line to get hung up on whatever you have on the foredeck. So you need to watch it as well as everything else for those few times when it is hung and it's not a fun day to go to the bow. It can cause a trip to the bow if you foul it but is can almost always unstick the clew so you can pull it clear.
Getting better with your tacks helps. Some of the big boats just plain can not tack without furling. I found light air was the worst. The tacking line is used less now than we used to, but still gets a tug once in a while. You can try that as it only costs a little to install.
Replacing the club foor with a roller is pretty nice but now we are talking some money
. It just helps to play with the stay sail and see how you use it in places where it works best for your type of sailing. A big genoa with a stay sail won't add all that much. Most every one I know with one likes it if when it gets nasty. Yesterday we had our stay sail furled part way with a double reef in the main. Some of the biggest Chesapeake Bay
chop I ever have been in with winds blowing 30 gusting to 40. The stay sail earned my respect. Rolling up a big genoa into a tiny sail really sucks.