The only time Ive performed what I consider to have been a for-real high-altitude takeoff, it went fine. I was at Albuquerque, N.M.s Double Eagle II airport, elevation some 5800 feet. It wasnt the middle of summer, but it was a warm, sunny fall afternoon. I dont recall which runway I used, but it offered more than enough length for my Debonair, which carried only me, some gear and full fuel. As Id been trained, I leaned the engine before the takeoff and let the airplane fly itself off the runway. I handled it gently until gaining enough airspeed to establish a proper climb and I had some altitude.