Anyone know where it is? My guess was the linkage center pivot point, my teacher agreed but wasn't 100%, material online seems to say the samething. I'm trying to figure it out because I found a cool setup for 67-69 F-bodies that uses a Watts Linkage and what appears to be cantilevered coilovers but the Watts Linkage mounts to the bottom of a Ford 9". Seems like this would be a really crappy roll center location even on a car. Neat setup though. http://www.uniqueperformanceproducts.com/CoiloverSuspension.aspx click on the rear coilover one. With the Watts linkage on top of or behind the axle I think this could be a good setup in a street/corner burner car. Namely make a nice donut car with the great side to side stability. Just thinking about the 69 Firebird dad has sitting in the driveway but never does anything with.