i don't know why but mine haven't been doing much. although they help me ride while my shinbang is still hurting lower down the shin, they haven't done much for prevention.
im riding Rampages, i replaced my power straps with boosters, i've tightened them over the plastic tounge part, under it right up against the tounge, and the spot that seemed to be doing the most, which was at an upward angle with all the buckles tightened i'd tighten it above all the plastic and on the upper 1inch of the tounge where it really locked all of the tounge to my shin, still even with that no luck- although i think my shins would be way worse with powder straps but who knows..
yes i got fitted at a bootfitter..