the bungee on this type of wing can't trap air unless you are upside-down. The bungee is on the bottom of the wing, the top is free to do whatever it wants. You have to remember that if this is your first time diving a horseshoe wing, if you are slightly head down which is normal with new doubles divers, the air can't equalize side to side. You have to go slightly vertical to get it to balance out. Remember that the inflator is on the left side of the wing, so if you aren't slightly vertical when you inflate, it will take the path of least resistance and go up into the left side and without a crossover at the bottom, won't equalize, even with, you have to get about the same head-down attitude as you would head up without a crossover.
This is inconvenient to some, a design error to others, but the lack of a crossover is actually fairly convenient if you are diving a DIR style rig with all of your stages/deco bottles on the left, or if you have any other sort of imbalance in your rig so you can balance out by packing air into one side or the other.
