Thank everyone for your input, much appreciated. Of course it's the rate of cooling which matters, no more than 50 ºF/min according to the Lycoming link. In airplanes we are taught a winter procedure for simulated engine failures: keep some power and lower some flaps to get an equivalent performance. Never heard that in helicopters, but we learn in an R22 with two POB, so simulated engine failures don't even last a minute, should be OK I guess...
However an R44 at 700 lbs below MTOW loves to glide! Better watch my CHT gauge next time. Even better, learn to anticipate arrivals before next winter
