So if you can't make the aeroplane climb, then it stands to reason then you are cruising at maximum power at about 100 kts. Remember in an airvan 1HP at the engine is about 6 fpm in rate of climb. I have flown in Botswana, and last time I sat in SAF she was cruising at 23/23 at about 110 kts. One pilot had her at nearly 120kts but that was 25/25. Now as I recall the 206 I also flew in in Botswana was running 23/23 and that was normally aspirated. The fuel flow meters seemed to be indicating 20US an hour at 23/23 which is about right. I've studied and applied the laws of aeronautics for 45 years,but if you know how a properly flown aeroplane can cruise on 75% power, but can't climb at 100% please enlighten me. Incidentally no pilot that I flew behind in Botswana climbed past the desired cruising altitude, set the power, and then pushed to a couple of knots above the desired cruising speed and let the aeroplane settle at the desired altitude and speed. And I've owned a PA28-180 with the orange band in the ASI so I know all about cruising piston singles