Regularly cruising between 7500ft - 10500ft in an R-44 in East Africa; 12500 ft up the slopes of Kilimanjaro a few times - collective tucked in the armpit, that is. Vibration is rather annoying at anything more than 65kts though and controls become somewhat insensitive up there, too.
Highest LZ in a 44 was ~7600ft (some 10,000ft DA) on a crater rim with 2 pax and 24gal of juice