Empire of Bones, p. 33: "Five-foot-deep recesses are located to the port and starboard of the dais, and walls of holoprojectors that stretch down from the ceiling surround each."
I've been staring at this sentence in the final encounter room description and the accompanying map for a couple days now. Luckily last night's session was cancelled so I have time to ask this question. Do the walls of holoprojectors extend all the way to the floor? Are the PCs able to pass under the holoprojectors and enter the pits or are these areas supposed to be completely blocked off?
My best guess is that they do not extend to the floor; it'd be hard to use it if it was entirely enclosed. I don't see why you shouldn't be able to get into the pit.
When I ran the encounter I changed the room slightly. I think that a 750 square foot 3D holofield would be significantly more valuable (and cool) if you get walk around in it, so I turned the ground into a single flat plane and turned the ceiling projectors into floor projectors.
Neither side really interacted with it in combat so I don't think it made much of a difference. The downside to this is that the PCs might not have as much mobility if Serovox's walls of force would have left a gap for the group to crawl under; but their a smart combatant. If they are able to angle the wall of force to not leave a gap through the projectors they will do so.