Where do you plan on putting the engine room? (not to get into another debate about where or how many there are supposed to be).
If you search around, you'll find deck plans of TOS Enterprise, both in finished, and partially finished stages, if you don't have a plan yet on layout ideas.
Your engine room somehow "feels" smaller than it should be. Maybe it's just the lens you're using on your camera. The back wall feels closer than it should be, even though you're matching the live action shot. I don't know. I could be loopy.