Slap the back of the head or punch?

[Larks]

Ok...we know what the book says is the signal for PC. The quesiton of the day is:

When A1 trucks over B1 (charge) when you signal prelim charge, do you punch (first straight out)or go behind the head as your signal?

On the floor, I punch. At the table reporting, I go behind the head.

Not asking what the book says here....I am asking WHAT YOU DO.

Ok then....Discuss