there's not 1 single answer for you unfortunately. just because you are getting shinbang in the stiffest tongue, that doesn't necessarily mean it's the wrong tongue for you- the shinbang could be caused by something else besides the tongue stiffness. go through this list and start checking things off that apply for you:
-no footbed
-boot is wrong size (usually too big than too small)
-continually landing backseat
-having a gap between the tongue of the boot and your shin, either because you have chicken legs or simply because the tongue just doesn't match up to your leg
-boots that are too soft for you
-boots that are too stiff for you
-boots that are too low on your leg
any of these sound like they could be contributing to your shinbang?