[aerohead]

[QUOTE=EcoVan;669500]I am mocking up the van belly pan with cardboard and hope to begin the real thing in about a month. I see that pop riveted screw nuts can help fasten materials to the frame/body, but how about fastening the belly pan material to other sheets of belly pan material? I need to make access ports for oil changes and greasing the front end so I need easily dismantled and reassembled joints.

The belly pan will be attached to the back bottom of the ABS air dam and then go back 4 to 7 feet.

I have some large sheets of coroplast that I can use if they are resilent enough to take some impact damage and then return back to shape. Otherwise I will need to get a sheet of ABS plastic... any recommendations for thickness?
One can make the access opening a little oversized.
If clearance above the panel allows it, attach angle aluminum, with a wide enough 'fin', all around the perimeter of the opening, such that from below, enough of that 'fin' projects into the opening, to allow attachment of the access panel.
The 'fin' can be pre-drilled, with speed-nuts attached to receive fasteners from below. Dzus fasteners.
If you are 'lifting' the vehicle for servicing, or have a 'pit', one side can be hinged, as on aircraft access panels.
Pop-rivets are okay for permanent attachments if they're installed with flat washers, to spread the load out over the coroplast.( Al just gave me 10-sheets of 18" by 24" of real estate sign coroplast for free ).: