Hi Jon,
I am in the Denver area and have a Whiplash Turbine helicopter, with a TS45i Heli Turbine Engine. Unfortunately, Turbine Solutions was no help when I asked if there was anything to be aware of at our elevation. Getting my engine to run was a major project. It did not work well with the supplied ECU parameters, and I had to experiment with ECU parameters to get it to start and run reliably. If your Xicoy engine is starting and running well, then you are in a much better position. Also, I found Xicoy a pleasure to deal with for a number of accessories that I purchased from them, so I would assume that they will give you great support.
One issue with my engine is that I found it very dependent on Air Density for it to startup and run well. I had problems on hot days (>90°) at the flying field. For it to work well, the Air Density must be greater than 0.950 kg/m3. I use the Density Altitude+ App on my iPhone to keep track of Air Density.
Frank