It is 1/4" Dow XPS fan fold sheets. Each section is 2' x 4'. I am using 3oz. e-glass which has an 8 loom weave making it flex fairly evenly.
I am going to need drain holes in the wheel strakes! The right side unit was on the car overnight, and we had heavy rain. It had about a quart of water in the bottom ...
It is good to get a fair bit done. I have them off the car again, so I can fiberglass the back of the main panel. I plan on pop riveting it onto the car (I hope the hold it, and don't pull through!) and I have small stainless screws and nuts to hold on the skirt. I'll fiberglass the nut onto the back.