Just recently an operator had a Bell instructor come to his base (MMTO at 8445 FTAMSL) to give them training in Bell 206 and 407, I just spoke to a couple of the pilots who got to do touchdowns at 8445 FT and they tell me the only noticable difference was that only more collective was required for every phase of the auto, but mostly at the end, but even then they never ran out of collective, just used more of it.
Density Altitude is usually above 10K there.