Interesting info! Should be no greater problem repainting the bays in aluminium.
I finished detailing the engine with some bits of plastic rod.
I then painted the engine in the suggested mix of black and steel. It looked to bright to my taste, and I did a black wash on some parts.
I repainted some parts with a darker mix.
Which I think looked much better.
It turned out that the "black" colour in the set, actually was a very dark metal.
Perhaps I should have used that one instead, but I'll leave it as it is as it creates a bit of contrast.
The guns also got some metallic paint.
Next I'll assemble the engine, and then I'll decide if I'll repaint the engine bay before mounting the engine.