"Yes, my concern is that a camera view from the top of the main stairway looking toward the gate might see the bottom of that hexagonal vertical shaft. So, I'd like to be able to include the gate room ceiling and the lower part of that shaft in this model. I can't find any schematics for that, nor any screengrabs of it. I can just omit it, but it would be nice to include."

Try this site: http://stargate.wikia.com/wiki/MGM_Tech_Journal
In the gallery section, 2nd row is an image of the floor of the jumper bay opening up into what looks like the gate room.

I can't really tell what's below the conference room but it looks like it could be a corridor but I can't find any concrete info. It's good to see I'm not the only hardcore Stargate fan here. :)

...... Kendra