The lazy jacks should end at about the lower spreaders. You'll probably want three-legs on your lazy jacks. Set them up so they look like this:
You'll need some 1/4" line, four 1" stainless steel rings, five padeyes, two small blocks, and two cleats.
I would install them with a padeye at the lower spreaders on the mast, with a small block to allow you to run the lazy jacks down the mast, so you can adjust their tension. Mount the two cleats on the mast so they lead fair to the blocks.
Run the line up the mast on each side, to the block and down, and tie it to a stainless steel ring. Mount the three padeyes at 3', 6' and 9' along the boom (assuming you have a 12' boom).
Tie two lines to the 9' padeye, run them through a ring and then tie them off at the 6' padeye. These line should be about nine feet long. They'll form the blue triangle above.
Next tie two lines to the 3' padeye and run them through a ring and tie them to the ring on the first line. These lines should be about thirteen feet long. These lines will form the red triangle above.
Last, run two lines up the mast, to the blocks, and then tie them to the ring on the second line. This will form the black line of the drawing above. Tighten the lines when you're dropping the sails, and then slacken them and lead them forward when you're out sailing. This way they won't chafe on the sail.
You may need to play with the line lengths a bit to find what works best on your boat and sail.
You could do this with blocks instead of rings, but on smaller boats, the rings work just as well and chafe the sails far less. They're also a lot less expensive.
IMHO, setting the lines up this way makes them the least likely to catch on the battens when dropping or raising the sails.
BTW, I generally will pop-rivet the padeyes to the boom or mast, rather than screw them, since the stainless steel pop-rivets are a simpler, faster, easier solution, and less prone to corrosion problems. Coat the pop rivets with lanocote or tefgel before putting them in place to help prevent galvanic corrosion between the stainless steel pop rivets and the aluminum mast. The cleats should be mounted using screws. Drill holes and tap them for the proper thread size. Use lanocote on the screws, to help protect the mast from galvanic corrosion problems.