Well.... here are some more ideas. Yes, slip them on before dumping the bags or putting out the slides for ease of sliding on. Go buy you some dowels that will slide through the grommets on the bottom (tape up one end so it won't go all the way through and get yourself some clips to snap on the other ends after you slide through behind the tire). This works really neat between the duals. So easy! And you know they can't blow away.
2001 Newmar Mtn Aire ISC Cummins on a Spartan, 2011 Jeep Grand Cherokee, Air Force One, Blue Ox