Brian, look for a z bar on any formula v (with swing axle). It's used to prevent jacking. I'm mixing terms. That's not the jacking you get with the adjustable spring heights on an oval car. It's the jacking that you try to avoid with a swing axle.
MadBill, you seem to be describing more than a z bar. You evidently have some means in mind to avoid use of the springs. You need to wave your hands more as you talk so I can understand. Wait a minute! I think it's coming through to me. You're considering the "free" state of the z bar to be with both ends down, so the z bar would act as the main suspension springs. Or, rather, the only front suspension springs. Then, with that z bar attached to the frame only at the center, there would be no roll stiffness. That's neat! But, I don't know if you could get enough of a torsion spring in such a short distance. You'd probably have to use 2 coil springs in torsion. Check around. Somebody's probably tried it on a garden tractor or golf cart. Would be an interesting car to drive. As you contact a bump with the LF, it would act as if the RF had also made contact. The more I think about it, the more of a monster it becomes! I'm thinking of dual coils in torsion with an arrangement through the centers of the coils to control lateral motion. Then, you'd have one wheel swinging forward and the other swinging backward. I'm afraid I'm just scratching the surface of possible problems that would be encountered in a long development time. All of this makes my suggestions seem much more straightforward.http://www.shopeshop.org