G'day Gerald, Interesting thread this! I am also very interested to here about possible turbine thrust gains at the lower ambient air temps.
I was running a PST J600/TEMS ecu on Thursday here in Southern Ontario on the test bench with an the ambient air temp -7c all went well, and the little turbine did not miss a beat....although I did not see any significant difference in thrust from warmer summer temps.
I would not hesitate to fly the J600 in these temps except for the frost bite factor to my fingers...and lack of skis for my ROO!