The rear (skipper) trap bungee doesn't go to the rear crossbar, it goes under the tramp.
There is a small block that gets tied to each shroud adjuster. You tie off the bungee to one side of the trap system, pass the bungee throuh the block on the shroud adjuster, then through the grommet in the tramp, under the tramp and up through the grommet on the opposite side of the boat, through the pulley tied off on the opposite shroud adjuster and tied off on the trap line on the opposite side.
You should probably just download the manual for the boat. http://2010.archive.hobiecat.com/support/pdfs/H20Manual.pdf