I'm sure this has been thrashed to bits before as a subject, but for a very good reason Auz military do not allow, and Brit mil recommend you don't, fly below 10 knots hyds out. Several lost helicopters have proven this around the world. Last time I was in McAlpines in Oxford there was a victim being repaired.
In the Gazelle days we had to take 2 pilots up below minus 10(?) degrees C due to Hyds out properties. Lower temp was possible by proof of performance at lower increments with 2 bods on the sticks.
Same reason Brit Mil do not fly thier BBs IFR single Pilot, it can take too long to get it down single pilot Hyds out before fatigue gets you.
(Expect a heap of tosh about friction nuts and more beans for breakfast but I'll ignore them in advance!)