Volume analysis is difficult, due to lack of data

I have temporarily been hung up on doing volume analysis in my program. I have the engine and boiler room volumes handled, but everything else is problemmatic. I SHOULD be able to do analysis on armament, but equipment and things like that seem out of reach, for now. The best I could do right now is to pull numbers out of the air. I'm not totally opposed to that, but I would rather do better.