I guess the skirts would be mounted inboard far enought so they don't interfere with the wenches and room for bungee hooks. I believe they just keep the air from falling back under the trailer where the front axle has to bust through after the tractor has already done it.
I'm 31/32 German but the 1/32 Irish in me entitles me to wear a kilt. I need to find one for St. Patty's Day and look out ladies when I'm climbing on my trailer!