What holds this crazy rig together? Why, abortion gussets, of course.

Fold a nine-inch wide strip of fabric (at 60″) into a strip four layers thick, seam its long edges, and then cut it into strips about six inches long.

Then seam the cut edges and voila – a little stack of stout reinforcements …

… to be sewn into place to keep the fabric all in one piece while still letting the air flow through.