Single layer --> Double layer

I'm not sure if anybody realised this, but all the structural structures (an oxymoron I know, basically meaning the sides, front and the back) are all of single layer, and this is not good enough. The doors are also of a single layer. Now I'll try to turn them into bilayers at least, so they look more realistic. I'll get somebody else to do all the undercarriage stuff, so I only need to worry about the body work.