easy to get into flutter territory if you don't watch your air speed up there
I spend a lot of time at high altitude in my 8 flying lean of peak and have never come close to overspeeding the plane. I use a 3 degree decent angle and just position the throttle to maintain my en route MP as I decend at 175-180 KTAS and about 800-900 fpm VVI.
I wonder if you could tell if there was more altitude to be reached with out dropping to far off the power curve? Do you think you were in the 60-70% of your H.P. range or below?
At 18,000 ft, you've climbed through about 50% of the atmosphere and have lost approximately 50% of your horsepower. I've been up at 17.5 with a heavy RV8, and there was still some climb performance left in it. Nothing to write home about though. The best reason I have for going above 10-12k is to catch better winds or get around build ups.
did you see a marked increase in "A.O.A." at that altitude?
If you are referring to angle of attack, yes, there should be some increase in angle of attack with increasing altitude provided TAS is the same as TAS at sea level. Is it "marked"? I guess it just depends on what you mean by that.
I did not run lean on peak at 17200, Joe because it seems that lean of peak and best power are very close at that altitude.
If temperatures weren't a factor, you would want to run at peak egt at low altitudes for best economy. As you climb higher though, temps fall off, and in the teens, I can run peak without getting over 340 CHT/1300 EGT. I use lean of peak to cool the motor at low altitudes (low being less than 12k). I never start LOP operations unless I start with a power setting below 75%. So far, so good (220 hrs).