The CaymanS bar will not fit
I have personal "butt" experience with the H&R rear bar, but I do not have numbers in comparison for it. I do know it is stiffer on full soft than the Tarett rear on full stiff. I have taken them out of several of our race cars. Just too stiff for some of the open diff cars.
My biggest issue right now is the rear drop links everyone sells for the rear bars. They are too short. Take a look under a Cayman Interseries car and notice the rear "pry bar" they have going on. The rear links are way way to short for those cars. Everyone sells a replacement heim based drop link for STOCK replacement. Stock replacement is GREAT for STOCK shocks/springs at euro or USA ride height, but when you lower the car, the upper link mounting point goes UP in the chassis!!! and in turn it points the rear bar into the SKY!!
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