Well this is an APC 5X5.5 speed prop(?), it is the prop I tried after the 6X5.5 used on the maiden. I went with a smaller prop on the second flight based on the idea that the 6 inch was too much disc load for the 3.17mm motor shaft, where the motor shaft bent during the first flight. For me prop selection has never been a critical factor with sport flying being my primary focus. Typically I looked at the thrust produced and worried little about top speed. At least with this plane I do have telemetry from the Castle Creations Ice ESC, so I have some idea of what my power and RPM figures are. It is that data which led me to a point in the flight where (during a diving pass) I saw the rpm peak at 29586 rpm with a real big dip in current (under 400 watts) ( this is where I thought I got my best speed).
The only thing I am sure of at this point is that I am not loading the motor anywhere near it's operational limit as far as power or rpm, and should be able to get a bit more performance out of the airframe. The next flight I have the motor timing set hard or advanced so I am going to be able to push more power through the motor, hoping to see a bit higher operational rpm.
With this airplane I am way out of my comfort zone as far as "knowing" what to do and am going to have to rely on the advice of those who have "been there" to tune it for optimum performance.