[Faster]

A permanent felt marker pen can last a while, or wrap a peice of light coloured tape and mark that.

 

[Faster]

...I didn't devise or propose the theory, I just know that many racers follow it...

Most racers, in fact, will have a folding propellor - whose orientation they check/fix (folded blades vertical) while racing to prevent a blade from "falling" open in real slow going.

I think the evidence is quite convincing that a free wheeling prop is less drag than a fixed; however some tranny's won't like it, and I don't like the noise so continue to lock the prop while sailing.