Oh!
i get it. 1st there are bunks, then the wall that is dividing fresh water tanks from the interior and theres the outer pressurehull. well, it would be difficult to indicate hatching, there is no point of drawing the water tank since it would close up the interior, however, when painting the pieces together, i guess i could paint that section light blue with the top edges slightly wavy to point out the water tank, i could also make a slight depression into mid bulkheads (0.3mm) and then simply let the paint roll into it. I guess i will do it that way. Will post the picture as soon as i make it.
In the mean time i made first attempt at the captains quarters, not finished yet, and i know that the rear wall should be a lot lower, though the dimensions would fall out dramatically, somehow i have to make a compromise here, feel free to suggest another solution.