On a double sided sail with a wishbone like mine  the out hall must be released to allow the wishbone to go up and down with the sail. The peak on a gaff must similarly be lowered to remove tension from the leech holding the jaws tight to the mast. Full length battens under tension are usually in batten slides wish bearings that allow them to move up and down a track I suppose battens could be placed in cambers like windsurfers and then the cambers could be fitted to rings something like goosenecks. The sail would then be under tension for and aft from batten end to luff ring and free to move up and down. Might work but not an elegant solution.I am sure there is a better one.I have seen designs that instead of goose neck like rings  use wish bone battens that extend for and aft of the mast .The rig is then also somewhat balanced like a junk Again I do not Know if it works.  Regards Tim