I drew it,... they built it. The people at 'Magicam' decided how it would be best supportable, considering how fragile the components were in the real (film) world of a one-g environment. As I recall, the top was left open to cool the lighting components and, yes, help suspend it. Besides, no high camera angles were envisioned so no top was necessary.
Thanks as always, Andrew. Is there any place where these drawings (or pics of the top of the model) have been published?
The other question I always had about the drydock is other than supporting a lot of lights and looking wonderously cool, what does it do?