
I did a little mockup of some ideas maybe for your windows and doors. You are doing a dark highlight on top to show shading and a light highlight on the inset windows and landings to show light, but the top down angle makes this a little odd as you probably wouldn't see the shadows from the top view.
Even if you could the color choice is really too strong.
1) The very dark line at the top is pulling the attention too strongly and it makes your window appear more straight on face to face. It's confusing to the eye on some level that doesn't read well IMO.
2) A suggestion for how to maybe fix this by simply removing the eye boggling shadow. Perhaps casting a darker yellow on the upper window line would work but the glass is so bright I think just leave it like this.
3) Same way for the door. That very dark line around the top and sides is making your door appear very flat straight face on to the viewer. I tried insinuating a deeper shadow line on the left-hand side as the door is likely deeper in than the windows.
4) I tried a bit deeper still on the door by sliding the door over to look more inside the ship. I'm not sure how this looks. Just some ideas.
5) The square windows have the same issue going on. If we are looking from 3/4s above you wouldn't see much shadowing on the window. The light from the window would be stronger anyway I would think from above.

I'm honestly not sure I follow the 20x10 on a circle concept. I may be explaining something wrong.
with a 32 pixel block you have certain scaling options that work well. Half of 32 is 16 so if you consider a single 32 pixel block to be 10 feet tall (by scale) 16 pixels would be 5 feet. You can use that to set up a full scale.
32 = 10 ft
16 = 5
8 = 2.5 ft
64 = 20 ft and so on
I hope this helps some. I think a circular window will still look circular but with the top down you just take into account the depth of your inset on the bottom lip/sill/landing.