Step 1: Carving Foam
DO NOT USE STYROFOAM. It compresses with any pressure applied and melts if you use anything aerosol to paint. I used latex paint. You can get good deals if you check the return section at a home improvement store.
The head dress is cardboard and a hole was cutout to cover with sheer fabric so you can see out. You can build this in two pieces if you'd like to make transportation easier.
Step 2: The Back of Olmec
So we installed tap lights behind opaque thin plastic red eyes made from plastic plates at the dollar store. The shoulder mounts are L brackets used for shelves, shoved into the thick foam and gorilla glued into place. nut and bolts were used to attach nylon strap that goes over your shoulders for support.
The mouth movement mechanism is made by taking a length of PVC pipe, adding an L connection, and a sharpened shorter piece of PVC that is stuck into the mouth piece in the back. Again...apply gorilla glue. Then you attach two of the C shaped brackets to the back of olmec, run the pipe through, and then attach a bungie to one of the holes in the PVC pipe you drilled to keep it closed. To open the mouth you simply pull down on the pipe.
The hip pipe is needed to keep the costume off your knees so you can walk easier. reenforce two brackets mounts on the sides depending on your box and 2" PVC pipe should work well. You can add pipe insulation to pad it for cheap.
We added fabric to the back and painted the lower portion to hide the mess and the wearer.
The head dress had wall paper texture sprayed on to roughen up the smooth cardboard finish and blend in. The round discs on the head dress and the "ear" area are the plastic liners you put under potted plants and only a few cents.