On Sunday, December 1, 2013 9:55:26 PM UTC-5, wrote:

Since I have been flying in wave at Minden for twenty years, caution with acro. High altitudes get you into the coffin corner especially with the higher speeds needed to maintain inverted flight,

Good point. This is less of a problem at 8000-10000 MSL.

and rotor turbulence can catch you at any altitude.

Very good point. Speed may be okay for smooth air, but too fast for turbulent air, and the transition can happen at any time (especially if you're spinning downwards.) In my limited experience, I've never encountered rotor once I was above the level where the wave forms.