Well, all I can tell you is that I did not pay attention to this particular aspect. I just made sure that the tape is flat, put the prop on it, tightened it and started the engine (of course I had balanced the prop before mounting it on the engine). Even at 9000 rpm the engine is silky smooth.
In addition, I have removed and reinstalled the prop several times (without making sure to put it back on in the exact same position), and I have never noticed more or less vibration, meaning that absolute precision is not needed when mounting a propeller this way.

Radial.