Starting a new build... something...

[Wombii]

Ahh, yes. That would explain it. These polystyrene materials are chemically the same as Styrofoam, but completely different in structure. They are not a foam at all. More like a credit card. I've only tried Evergreen, but Plastruct is another popular hobby brand. You may be able to find the same material in large sheets from a plastics material distributor or a store for construction materials. I like it because it's easy to cut (score with a knife, then bend to break it off) and makes a very solid bond with a solvent based glue. I don't have experience or a suitable work space for working with metals, but you seem to be good with it. I'm sure you can make a very nice metal cab if you prefer that. Brass is a popular material for detailed work as it can be soldered with normal tools.

This is a good intro to working with styrene: https://www.youtube.com/watch?v=uJQ71o1qqWw