Dunno about sails, but when I get fibreglass framed kites they just roll the spars up into a curve. I realize that cant happen for carbon tube battens but the fibre glass ones will curve into the 105mm x105mm x 100mm that Aussie post has handled for me. (a 4.2m2 C Quad from Melbourne) cost $17.25 registered post to Esperance.
Just some food for thought.