Alan and I participate in most of the New England shows that are defined as Corvettes-only, judged "show & shine" shows. That means that there are only Corvettes, that the Corvettes are broken down into classes so you are competing against similar cars, also broken down into coupes and convertibles, and the judges grade you on multiple items, but everything is based primarily on cleanliness and secondly on condition. Standard rules here in New England for these types of shows are:
Windows up
Tops on or up
Everything (and I mean everything!) out of the car
Stay with your car but do not talk to judges at all nor will they speak to you except to ask you to open the doors.
On less formal shows, I think you can leave the mats in!
Elaine