Too many people think that a TB such as ~1.12, 1.15, 1.18... 1.2, 1.22, 1.24 are really stiff. From my experience, and I've tried progressively larger TBs in my past while developing my Challenger (for serious E/SP SCCA competition), sure, they get stiffer. But even at the 1.20 and up range, their not SO stiff that they'd be unbearable to drive on the street/hwy, etc. SMOOTH roads and surfaces (not constant bumpy streets, etc), are not so rough at all. Typical AX/HSAX/HPDE roads/surfaces are SMOOTH, therefore, they can easily justify stiff TBs. But, IF you're concerned for road gripping on progressively bumpy roads/surfaces, then use softer TBs.

If my info is correct, the actual SCCA Posey and Gurney Trans Am cars use ~1.4" diameter TBs (using ~C-body hexes). I've seen those cars run on road courses... the fronts re pretty flat from lift/dive/lean and then... the rear leaf are extremely stiff (don't know their rates)... but have multiple leafs... like truck springs... and flattened.

I emphasize the advantage of stiffer TBs to reduce lift/dive and lean. Fine tuning the "ride" can be done with shocks (ultimately, consider the latest generations of adjustable shocks... Viking, QA1.. double adjustables, along with tire PSI, and considering tire sidewall height.... rubber band tires, such as 30-35-40 profiles, have progressively little sidewall cushioning, giving a more harsh ride.

If you can avoid bumpy roads/streets, pot holes, etc, regardless of your suspension setup, try to avoid them... no fun for "handling"... unless you drive an off-road setup truck.