I built the same kinda thing FlyinBeagle did.  The wings are on the bottom and standing on the LE.  I have 2 crossmembers on top that swing away so that I have easy access to the wings.  I simply did not cement the crossmembers so that they can move.  Padding and velcro everywhere.  I do not have a 7 ft wing yet but it will fit with the tailgate open.  I bungee the whole assembly to the truck.