In my opinion, any torsion bar over an inch begins to transfer significant flex to the chassis as the suspension becomes less compliant. I don't have specific data to confirm this, but road feel over several vehicles using various bars.
I agree with this although I have no actual science to back it up.
For me, common sense tells me that the Mopar unibody structure and suspension was all engineered around shared compliance. Looking at it this way, the frame structure was designed to support the suspension and spring rates as designed. Once individual components are UPsized, the structure will start to flex more. Imagine everything stock except with wider, stickier tires. Now the car does corner a little better but the body leans/rolls more because the tires are gripping but the torsion bars and sway bar are more stressed. Now upgrade to larger torsion bars, sway bars and shocks. The car corners even better but it sometimes feels a little unstable on uneven surfaces. This could be because the unibody structure has now become stressed because the suspension is far stiffer than before.
