Looks like 1986 was a factory drawing change to a single boom bale at what looks like 81.5 inches aft of the forward end of the extrusion. They also tilted that bale forward 13 degrees in 1988. We have since revised this dimension further, but I can't place a drawing at the moment. To use the current / latest dimension, you should use the latest step casting and base though. They allow max rake and that started with the 2004 Worlds boats.