I forgot to mention that i did try a bunch of prop and test power draw on each and just did a crude hand held thrust assessment.
the 3D printed props did well IMO and the best one i made perfectly smooth and out of PC MAX a poly carbonate 3D print material which was super strong / stiff.
I also purchased a FR 6" pitch prop for comparison as well and tried that. Its a work of art and definitely gave me more efficiency, more top end speed and more thrust than my best 3D printed prop.
The FR is expensive vs printing something for almost nothing BUT with all the effort we go to to get out of the water and the power we put into the motor i cant see the point in running printed parts when there is so much to gain from a proper machined part. IMO and testing anyway.
but it way a lot of fun to play with printed props. that all being said the printed prop would be safer for learners as it has a very rounded LEdge