You know that's a great question! Sorry for the late reply. I eyeball the scale based off windows, and then adjust certain decks that are further back. These photos are taken in Star Trek Online, then put into Affinity. Outlines of the ship are hand-drawn at 6pt.
I've attached the update of the Nova class (the Equinox Class) I hope this helps!
I will work on this version next! I'm almost finished with a new class that was also a request...