Had a chance to run by Home Depot near the hotel and did some serious shopping. Went through the isles looking fer the right material to brace the upper rear wheel with. Looked at corner beading, wood trims, floor tile guides, and modular shelf bracket rails. Eventually settled on the modular shelf bracket rails as it would be easy enough to shape by hand but stiff enough where the air wouldn't be able to deform it.
With the slots in the bracket rail, I found it much easier to zip tie the Coroplast panels on. I ended up using a couple extra zip ties on the lower rear wheel skirt panel so it would keep the preferred tapered shape.
I did figure out why the supports rubbed...it was from the extra passengers and cargo. When I put the rear wheel skirt supports in, I didn't account fer how much the back end would drop down when loaded. At least I won't have to worry about that now.
I'll have to upload piccies of what I changed when I git back home if I don't find a way of downloading my piccies to my Photobucket account.
On a side note...someone from Puerto Rico did take a picture of my truck with their family and myself.