It took a few tries before I was happy.

My lower spreaders are too low to get a good angle if the jacks only go that high. Jacks need to be out of the way except when dropping the main for the reasons written in other posts. The other issue is that I hate having lines slap on the mast - hard on the paint and noisy when trying to sleep. My ultimate solution was to put the mast blocks quite a bit above the lower spreader and put some hooks about half way out on the aft edges of the spreaders. The lazy jacks are hooked on the spreader hooks and on the boom reefing hooks when not in use.

Before dropping the main the jacks are taken off the hooks and pulled into the proper position. I leave them fairly loose so the sail coming down spreads out a bit - not just coming down into a very narrow space. Once the main is down and the boat in on the hook or in it's slip I slacken the jacks even more to neatly fold the main. After folding and tying the main on the boom the lazy jacks are stored away on the hooks until the next time.

Just tying loops is OK for trial and revision. Metal rings are hard on the boom paint when stowed. I use very thin line, about 4 mm. Ronstan makes nice little blocks that are much better than rings. They are all plastic except for the sheave axle - no scratching the paint and smooth running. It's been set up this way for about five years now and those little blocks have held up fine. They are very small and rated at IIRC 150 pounds working load and to look at them it is hard to believe that.