Hi Jon,
Here is a link to ERA's website showing a photo and description of the Coremat Lippy mentioned.
Assembly jig
On the finished body, it is glassed in. Looking up in the fender well, you can see the outline of it as it is a bit thicker than the surrounding areas. It might be a bigger project than you intended on to glass it in but it would absolutely stop any body damage.
Regards,
Kevin