Grinding Bootboards

I just picked up a pair of Atomic M11 boots. My left ankle has been sprained so many times skateboarding that my left instep is way bigger than my right one...and big enough that the toe box is too short around my instep. I figured grinding a little off the bootboard would fix my problem, but how the F do I get the thing out of the shell...seems fixed in there with glue.

a few vintages of atomics are glued in.

and you thin the footbed?

if not open the side stiching of the tounge and remove some padding on that?