its not about just the high back. its about how tall the high back is, how tall the heel cup is, and where the straps attach to the base. The higher up your ankle strap attaches to the base the more response you will have. Just becuae a high back doesnt feel stiff doesnt mean the binding will be soft. the shape and size of the high back makes a big difference, and yess union bindings r stiff. my buddy who rode flux super titans ( a stiffer flux binding geared more toward tranny riding won some union force bindings and he said they were a lot stiffer, he did like them but he wasnt a super jib dude either.