RE: Speed props – a difficult task
For the most part yes. I've seen venturi's checked for proper diameter, plane weights checked, motors torn down, etc..
If you tried to cheat on a national level, you would eventually be caught. The prop situation the past couple years may be a different story.
Unfortunately there was enough variance from prop pitch from one prop to another, that it was very difficult to tell if someone de-pitched a APC black plastic prop. The initial props were a tad on the heavy side and only the stronger motors and better local conditions would really let you get the best out of the props.
However, this spring, Fred B. at APC got several lighter props approved that work well in bad conditions, with the new LS motor, the Jett Motors, and even older less competitive motors. Twisting props now is completely unnessesary as you have plenty of sizes and variance to work with.