Where does the forehead end for bald people?

Where the baseball cap begins.

The small of their backs, where there is usually a tuft of crack hair

At the crown, the part where the skull stops going up and starts curving back.

Foreheads wrinkle when you frown, hairless scalps do not. Edit: headless -> hairless

Where it ends for most people, at the edge of their scalp. The area where the hair used to be when it was still growing

It never ends, unlike the hair.

You just keep adding 1, so it becomes a fivehead, then a sixhead all the way up to slaphead.

Coccyx.

A fourhead is only as far as four finger widths from your eyebrows. I myself have a fivehead.

At the start of the five-head.

It just goes all the way round. Bald men are literally dickheads.

End?

At the mullet

If standing straight, roughly at 110° from the floor.

Directly above the asscrack.

Directly above the asscrack.