FFB, Thanks for the free lesson. I am already aware of the overhead joining procedure (since I was first taught and practiced it in 1973) and subsequently taught it to RAF SEP students.
The problem I was trying to highlight is that (irrespective of where you want to call the actual overhead position) two aircraft could be heading for the same point in space at the same time without prior warning. As far as sequencing goes, one pilot might call early, the other in the ideal position, or slightly late. Lookout, effective use of the radio and common sense/airmanship are the answer to keeping it safe for everyone.