I'm an Ocala, FL guy like Rick also, however I spent almost 4 years at KAPA, Centennial Airport, South side of Denver, CO, with my at the time Brand new Beta II. Elevation was 5,866msl. On summer days of 95 degrees plus, the machine would be working real hard with Density Altitudes of 10,000 or so.
As an old guy of over 20,000 hours in the air (about 1,100 in copters), I played it real cool.
I generally would go out a day or two early via car, and scope out the area for all the safety aspects.
I expect this isn't quite what you want to hear, but it did work well for me.
If I thought it was doable, I would then fly an approach into the place solo, early in the day for best temperatures, and usually minimum wind. If things were comfortable, I would then consider a very lightweight passenger and minimum fuel on the next attempt.
It worked well and no bad things ever happened. I always had an escape route out of the place on landing, and takeoffs, I would always keep in the back of my mind, the other guy can always get out if necessary and I would pick him up a short distance down the road as he would start walking.
I'm sure this is stuff you already know, but it kept me safe.
By the way, as to the power check issue, at these elevations, you simply used everything you had, which on a real good day, you might get near the max. manifold pressure, but because of the altitude, you often didn't.
The most important thing was being smooth with the machine, and smart with the brain (don't try something that obviously is beyond your capabilities or the machine's)! I guess that falls under the preflight planning part of the FAR's, obtaining all available information before flight?
N222JA R22 Beta II