We have a near-new UK Lazycradle. Works great. They designed the 'lazy jack support' lines so that they hold up the full length battens on each side of the zipper opening and do support the covered sail all the way to the end.
It's a good design, imho.
We have no lines to the end of the boom, in any case, altho the main halyard is clipped there to 'lock' the boom into place when the sail is furled. Our boat came with a standard rod vang, which holds up the boom without a problem.
Fair winds.
Loren