If I had a choice to locate the dampers, I would say that on top of the axle, like landrover did is best. The axle tramp may be a reason not to, but the forces on the bushes trying to counteract the damper forces are pretty big. To put it in perspective, in a dynamic situation, driving fast over potholes, the peak forces on the damper are much greater than on the springs. Landrover understood this on the first rangerovers, where the rear dampers were asymetrical, one pointing forward, one pointing backwards to counter act the forces.
I went for the shocks on top of the axle on every corner, and I like the setup very much.
daan