From my experiece, (I had my payment at the P4 position)I would suggest Positions P1 - P4 ( Follow the blue links )
They are on the back of the hand, The benefit is, the skin is thin, so good for reading, and because they are on the hand, you get maximum mobility to present to a reader.
The back of the wrist ~where you would wear a watch (Avoid the watch side if you wear one) is a good alternative, but the skin is slightly thicker and you don’t have the same mobility as the hand.
Happy to discuss further, also, other people here may give their suggestions / experience