Probably not accordian... I'm not sure how I'd make that.
I'm thinking that I'll affix a strip of velcro to the rim of the bed, so while the shell's down, the side skirt can hang down inside the bed, and when I put it up, the skirt'll just velcro around the edge. I've thought about using a bit of elastic cord to put tension on the skirt so that, once it's un-velcroed, it pulls itself out of the way of the shell when it's lowered.
Attached is the most horrible-est drawing i could make :P
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