I figured it out with youtube videos, taking screenshots of each top-down view over the years.*
In theory the center of the spot is (normally) on the line between the 2nd diamonds.
So I just drew a line between those diamonds to see where it crossed the rack.
*couldn't find 2001 footage.
I'd say 1999 is when they first started racking high, and it kept creeping forward over the years
until finally finally the 9 is fully on the spot in 2004.
It's not very consistent... unless the camera is playing tricks the placement changes a little
every year and maybe from rack to rack. In fact in some footage it's hard to see the spot and
I half wonder if the ref isn't eyeballing it. Hard to be consistent if the rack placement varies.
1998 is the last year it was clearly racked normally, line passes right through the middle of the 1.
Then it's a ball high in 1999, 1.5 balls high in 2000, (2001?), 2002.
Around 2003 it's 2 balls high, front of the 9 touches the line. 2004 the 9 is definitely on the line.