I've heard that full battens hang up on lazyjacks a bit too often when raising a mainsail. To remedy that problem some have anchored the top end of the jacks to the spreaders, creating a "V". I'll be trying this approach on a new rig next Spring.
My lazyjacks are threaded thru holes a little ways out on the spreaders, but not sure it helps that muck; they can still snag the batten ends. When ordering my Mackpack, Mack cautioned me that under some conditions (off the wind) if the lazyjacks are attached too far out there may be an undesirable force on the spreader that it is not designed for.