Ha! Good catch, Kendra. From that infographic picture, I can see the relative size of the shaft, and I can see the dais below. (The "dais" being the slightly elevated platform with the gate at one end and the bottom of the main staircase at the other end.) That's enough for me to work from. The gate room ceiling and the bottom of the jumper bay shaft definitely need to be removable, for camera access.

I have lower level (gate room floor level) and mezzanine (2nd floor) plans. Angular first floor walls run under the middle of the conference room, and that first floor wall has a door. I may simply leave that door with nothing outside of it, or I may make a holograph room there, since the holo room has circular walls (at least on one half) like the conference room. The holo room is where Ganos Lal (alias Morgan LaFey) appeared to Daniel Jackson, pretending to be a hologram. Black lines are lower level walls; green lines are upper level walls:

I've projected a schematic onto a primitive ring, to guide me in making cuts/extrusions. Don't worry, the stargate won't look like that when finished! I have a chevron formed, but not UV mapped yet.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5