Drop Ceiling and Upper Valence

I finally got around to figuring out what was needed for a drop ceiling in the layout room. I am trying for two levels. It is made complicated by an already low ceiling and duct work in the way. I made some measurements and the best I could do would be 6' 4", which would be unacceptable for a single height ceiling.
The first thing I did was move the ventilation around to the perimeter of the room. This gave me more height in the middle of the room. I then had to build a valence over one side of the layout to hide the duct work and lights. This turned out to be about 6' 3", which is OK because it is over the edge of the layout. The upper level might only have about 11" of clearance. This is not as good as I want, but a single deck layout is just not acceptable at this time.
I will set up a temporary upper deck and play with the heights and clearances and see how it looks. The area I'm most concerned with is just going to be countryside. This might be a slightly lower, lower deck, but we'll see how it goes. If it turns out that I can live with the clearances, then I'll decide if I have a valence all the way around the room.