My mistake- the 175 watt units are good to 15,000 MSL, 200+ watts necessary above that. So, Moriarty and most high altitude western US sites with potential flight altitudes to 17,999 MSL (and higher in ARTCC authorized airspace such as wave windows or SAGE II clearance in the Sierra Nevada Wave etc.) would imply utilization of the higher transmit power of the TT22 over the TT21.