Fastening coroplast to the underbody
 

I ordered the coroplast for the Matrix last night and it should be in sometime today. So, I've been thinking about how I want to fasten it to the body. I don't want to squish it, but I need the bolts to stay in. So, I was thinking about using some bushings. How have you guys fastened coroplast to your body?

I'm looking at using push-ins where I need to mount Coroplast and have access to the other side. Some are acorn pushins and some look like a flat piece of metal stamped with a hole that will accept a screw but still keep some tension on it so it won't back out. You could just add a spring on a screw or mount a grommet on the coroplast and hang it with a spring. I'm still exploring ideas too.

You can find or modify finishing washers to provide a flat flange around a countersunk screwhead. If you can't find any, drill and countersink a chunk of scrap, and then pound regular finishing washers.