Hi Mark,
I know this design is very preliminary and I assume you know, but I thought I'd mention it just in case, that your lower level track is set to a height of 2.99" and the upper level to 6.1". Obviously, this will not work. 
You also have your upper level track crossing over itself on the curves in the lower left section. Do you intend to have an over/under grade there or a crossing? The over/under on supports might be a challenge, but if your intent was a crossing, I don't believe Ross makes a curved one and the standard straight ones will change the upper level geometry.
You mentioned using GarGraves track with Ross switches. You're currently using GG switches, so I thought I'd also mention that the footprint of the Ross switches is quite different. I added a Ross O54 just to show you the difference in size. I used the GG O54 you had and didn't play with O42 or O72.
I hope you don't mind, but I also played around a bit to see what an over/under would look like on the upper level and added a crossover to the lower level because it looked like you were leaning in that direction. I wasn't sure of the layout size inside the room, so I just used 138x115. I look forward to seeing where this goes.
