I reported on mine in another thread but didn’t update this one. (See Help debugging setting VTX Power via SmartAudio? Debug logs included - #6 by cbf123)
I ended up using an Arduino Nano as an oscilloscope and discovered that this VTX is using a single stop bit instead of the two that the spec calls for. (Incidentally, I checked with TBS and they said that Rush had only ever sent in the Tank Solo for testing, which might explain why this one doesn’t match the official SmartAudio spec.)
I’m not home so I can’t check my settings, but I believe I had to use the “RX pull up” setting since otherwise the VTX would send very low-voltage signals in response. (And it has to be set when the VTX is powered on, you can’t change that setting on the fly.)
With those changes I was at least able to switch between pit mode and normal power, but as I recall it was still slightly flaky when changing power levels. (Haven’t been able to work on the model for the last month or so.)