panels

Could you give me recommendations on the best way to attach interior panels without having screw heads exposed (roof panel, a pillars and door side panels)?

For almost 18 month, I am working on my mixed KVA (panels) and SGT (chassis) MKI project, feeding a blog in German so far. Since still people are reading my stuff, I decided to also let the world know what I am doing in my spare time. It all starts with really bad panels, that I bought for a...