Foamcore for the coffins themselves, definitely. As for the support, wood is definitely a good choice if you can find a type light enough. To get the angles you want, perhaps try PVC connectors?
DeviantART // Tumblr // Facebook // Instagram // YouTube
- Judal (Magi: Labyrinth of Magic): 16% (Wig Overhaul) Katsucon 2017
- Galaxy Print Shiro (Voltron, Original Design): 70% (Arm Work) Katsucon 2017
- Blanche (Pokemon GO): 82% (Sewing) Katsucon 2017
- Lelouch [Emperor Robes] (Code Geass) : 4% (Patterning) 2017