My lazy jacks use brass rings instead of blocks. Way way cheaper, cuts any chafe to zero, and work fine. They are rigged to a cheek block about half way between spreader and mast head and the line running back down to a cleat at the mast. Very easy to store by slacking the lift line, pulling the jacks forward, hooking under the cleat and then cinching up the lift line. Disagree that using the spreaders works well. Even though mine are higher on the mast, the aft section of sail sometimes isn't captured by the jack line. A smaller angle between boom and jackline would make capturing the aft part of the sail iffy on my boat. Boom is 16' long BTW. Have sailed on one boat with the lift line to the mast fixed and adjustment at the boom. Did not like that setup. Used way too much hardware and stowing the lines at the mast was too involved.

Always sail with the LJ's stowed at the mast. Only deploy them to drop the main. Tried raising the sail with them deployed but usually hooked the upper full batten no matter how careful I was about keeping the boat into the wind. Have had the same problem with LJ's on other boats I've sailed on. Don't like the LJ's banging around on the sail underway in any case. It's super easy to stow them at the mast so no big deal.