in my opinion map reading does nothing for setting the prop. rpm on the other hand. I have the round guage with color code for the 912. very nice and I keep it in the yellow on take off or 5800 area for no more than 3 minutes. after that it stays at around 5200 regardless of the throttle. at least to a point. when I go to land I put full throttle at 5200. than I back off the throttle to 4200rpm than flatten the prop to 5200 about a count of 3 as in 1000-1 1000-2 1000-3, generally that's all it takes. If for some reason it takes much longer than that, it's a sign the prop movement is slowing, I start looking at things, yes this has happened, I found a build up of grease on the contacts where things spin, for the brushes. I leave the prop setting alone and when I go to take off the next time it's perfect for take off. I monitor the rpm and operate the switch for the prop to stay in the yellow, once I level I put it to 5200. done.