I catch the drift of your post BritBrat, et. al. My gut reaction is there is a scale factor here in play, which may explain why the issue seems to be basically moot on large people carrying planes. The small electric I tested has a large prop compared to wing span and a lot of power for the airframe size too. It is also operating at a much lower reynolds number than any people carrying plane. This may be a significant factor. I also believe that if the spiral slip stram factor does exist, is velocity dependent, i.e. it is most significant at zero forward airspeed, as in my lazy susan test. I however have no proof other than my gut reaction based loosely on a semi-educated guess. While I keep pushing the spiral slip stream idea, I'm still not convinced spiral slip is a major player, and indeed it might all be p-factor, even with the models, but the lazy susan test has me second guessing myself as the results were more dramatic than I expected. I'm wondering if maybe the test apparatus interfered with airflow. I plan on retesting again in such a way to eliminate that possiblity this evening. I will post my results. Cheers.