Technical Split rear bones - design change

Question,

Split rear bones, last T speedster chassis I built with split rear wish bones. There were the following particulars:

1. Used early B stamped end wishbones, cut and shortened with A tie rod ends, retained the T torque tube behind a warford and used a 26/27 rear end.
2. Length, don't recall exactly, but about 36"
3. The front pivot point was set at the horizontal center line of u-joint at the out side of the frame. Which represents ~14" linear difference to the anterior and a 4" movement forward of the normal mounting point behind the ball joint.
4. Very stiff rear spring, 11 leaves, this was due to the rear drop i built which had the effect of having an increased leverage (centerline of rear axle was 4" behind the centerline of the spring)
5. Model T frames flex a lot
6. The rear did not bind, probably more due #4, it still moved freely, but could get very tail happy.
7. I bent each wishbone to into a 1/2 a parabola shape, effectively lengthening each one over a

At the time, race cars at the time split the bones to provide for a stiffer rear triangle and control lateral movement of the rear axle, period perfect aesthetics can be a compromised today.

Observing more builds (not Speedsters), where the rear wishbones are still split, but mounted closer to the center line and the u-joint. Maybe 4" to either side? Why (more arc)? This seems logical (but not easy on a T) and I can always put a panhard bar on back to help with lateral control.

The new build will be using a TT frame, which is whole lot stiffer (less flex) and I really don't want to start snapping wishbones as the load could be isolated in them and become the failure point.

Thanks,