I don't know very much about electric setups, but if RPMs go up and current draw go down [and you aren't in a dive]...I would suspect that the shaft is spinning faster than the prop.

Every APC prop I've tried in a speed application has delivered real world MPH numbers that matched the theoretic [projected] speed pretty closely.

The biggest anamolies I've heard of with their props is how the 9 x 7 sport prop out runs the numbers on Q500 planes....

and the 10 x 7 sport prop on a Patriot was shown [in a RCU thread] to behave more like a prop with more pitch.