I've tried checking my PAP by putting on a piece of tape, but never can be positive (my eyes must be going...)
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I noticed while watching a Hi-SP video that Akio Ishihara always has a length of tape on his ball. For me, I can easily see that his PAP is correct using this method, which of course would let me measure rev rate as well. I was very impressed with how much easier it is (for me at least) to check PAP this way.
I think the tape goes from PAP to above fingers, but what type of tape? I was thinking painter's tape so that I leave no residue, but can't find white. 1 inch adhesive tape would leave residue... What type of tape would you guys suggest?