Ok now I'm getting somewhere with the prop test on my Legacy 40. But... When I started testing I tried a 11.5x6ep. I got the lap times where it felt pretty good although the Castle motor data said the motor was running at 96% power out. So I said lets see what it does with a 11x5.5ep. I had to crank the rpm's up to 1050rpm to get the lap time back to 5.2 sec. The castle data showed less current but still running in the high 90% power out. So just for kicks I was going to try a 12x6ep and a 11.25x6ep and see where I was. I started with the 11.25x6ep and lo and behold I had to drop down to 8720 rpm with 5 sec.laps and at 86% power out. Next time out I will go lower rpm on the 11.25x6ep so I can slow the lap time down.
 I wasn't expecting these results. Is it possible that the motor is breaking in and becoming more efficient? I didn't get to test the 12x6ep because of the approaching storm.
                                        Bob

Hi Bob,
Could it be that the source of your confusion is that the data-logger reports "% Power"?
That's what the label says, but it's not really power: it's % battery voltage (or duty-cycle for those that care).
You can run very different powers with the same percentage of battery voltage, you simply add more prop load.
Yes, electric motors make more power the harder you load them ... until they over-current and melt. This is backwards of what you have always known.
You kept adding prop load and lowering the RPM as needed, but the power going to the prop probably increased with each prop change you described, even though the datalogger says it used less voltage.
Now, if you were to compare the battery capacity used for each prop, and the peak amps in a climb, you'd see that the largest capacity used and the highest peak amps in a climb all translate to line tension and control authority when and where it counts.
Hope that helps,
  Dean

Yes, Bob ...
call it percentage of the operating range if you like ... percentage of the battery voltage is more precise but means the same thing.
You do want to get into the low 80's (even high 70's in my opinion) and that only happenbs with more pitch and lower RPM. Lately you may have read threads where folks are swapping to 5S because they feel better punch coming out of corners leading into climbs. This is because they added almost 20% to that voltage overhead that I like mto keep near 30% rather than the 4%  or 105 you reported earlier on in this thread. That voltage overhead is what is available for brief impulses of lots of torque that will fight RPM bog during draggy corners.
take care,
  Dean