That top head is designed to screw in to a hole. This way the the panel is sandwiched between the two "heads". If you ABS is 1/8" thick or so, the clips should work just fine. Get a scrap piece of ABS and drill a progressively bigger hole until the clip fits/works. Then, with all your holes drilled in your panel, place the panel on the door and mark / drill the corresponding holes which will be a slightly smaller diameter than your barbed shaft. Every 8-10" should work and the corners. Maybe even some in the middle of the panel in strategic places. After you cover your panel in fabric, you'll have no visible clips. And, if they break, they are easy and cheap to replace. It does help to have the specific fork tool to help remove the panel when you need to.
