Ok, so here is the gist of it... I drew this up in Paint in about 5 minutes, so that I wouldn't have to take off the grill block and take it apart to show what is on the inside and how it all worked out. I'm not sure if anybody will understand this drawing, but I hope you get it. It also wouldn't hurt to add a verticle support (like on the sides) to the center. The fishing line is to keep the 2 pivot points (on the rear sides) from backing out of the coroplast without limiting their ability to rotate.
I have attached a few pics of the real thing as well.
