For structural pieces, you need THICK cast couveture--at least 1/2" thick. You can use many things, including sausage casing, surgical latex tubing, vinyl tubing, and, um, ah,... "those funny balloons" that you find at the family planning section at drugstore....
With such items filled with tempered couvture, you can wrap the the tube around cake forms, free forms, etc, and blast off in the freezer for a minute or two.
Another possibility other than chocolate is croquant. This is nothing more than two parts carmelized sugar to one part flaked almonds. When this mixture is still hot you can rollit out to desired thickness beween two sheets of silicone paper and cut, shape or form while still hot. When cold it has the same properties as glass--very strong and very brittle. I have made many logos, signs, showpieces, etc. with this material. Over 3/8" thick is very strong and won't melt in sunlight or halogen lighting, but it does need to be sealed with a food grade laquer so humidity won't soften it. g2 gas
