Do I understand you right that when MidPoint is set:
to 7 you get mostly head when you hit rim.
to 8 you get mostly head when you hit rim.
to 9 you get mostly head when you hit rim.
to 10 you get mostly head when you hit rim.
to 11 you get mostly head when you hit rim.
to 12 you get mostly head when you hit rim.
to 13 you get mostly head when you hit rim.
to 14 you get mostly head when you hit rim.
to 15 you get only rim when you hit rim and you get mostly rim when you hit head.
?