Javelin for NASA American Iron

[68protouring454]

nice job.
Ideally you want the rear roll center as low as possible, however that generally goes with higher spring rates to keep the car balanced.
How long is your phb? center to center? The center of it is the rc of the rear of the car, so you want to get the phb as long as possible to put the rc in the middle of the car,so that the forces on the springs and shocks are even side to side. Thats why watts links are so good for road racing in a stick axle application.
I would never go higher then axle centerline for the phb height, however you will need to stiffen the springs/shocks as you lower the phb or you will just create more of a push.