That post got my head spinning too . My first thought was like yours. The reduced engine power should turn the same prop at the same rpm because of the reduced prop load in the thin air. My second thought is that I do not want to think about it any more because it makes my head hurt. I would like to find an article that gave exact #'s from the same engine at different elevations using different nitro % and props. Combatpigg, see what you started![>:]