shinbang-ish snowboard boot issue
I'm having a persisting issue with my snowboard boots where I end up with my shin worn raw on my back leg. All I can find online is "shin bang", which seems to be somewhat muscle/bruise related and resulting from back-seat skiing. I'm having some sort of rubbing issue on my shin bone and as I'm a snowboarder the "don't be backseat" advice is harder to apply.
I'm riding in old and fairly packed out Burton Diver x boots (pretty stiff). I think they are about 9 years old but maybe with only 60~ days on them. I have a little bit of heel lift-off issues and tried throwing green superfeet in there to take up some volume but it didn't improve much of anything. I'm open to replacing these (and possibly going a size down) but want to make sure I understand my problem and eliminate it in the process. I find it unusual that it is only happening on my back leg.
The other variable I'm considering tweaking is my stance width as I notice that the rubbing is slightly on the inside and I've got the bindings one notch outside of the reference position marked on the board (both bindings one position out).
If anyone has any experience with this or recommendations of variables I might want to tweak please chime in.