Maybe I wasn't understanding the role of the fairleads, as you described. I thought rope would run through, and that's why I suggested blocks.

I also don't see any downside to moving the attachments out further on the spreaders, several feet not inches. The further out they are, the less they'll interfere with the sails in use... And the less you'll need to slacken them when underway. Mine are mounted on both the upper and lower spreaders several feet away from the mast and I never adjust the lazy jacks except to adjust where the boom rests when the sails are lowered. (My lazy jacks do double duty as a topping lift, because topping lifts interfere with high-roach mains).