Have you tried dropping the level of your bootboard?
I ask this because I wish manufacturers would make bootboard modifications easier. First, make all bootboards with a flat level surface. Please don't put any curves on a bootboard that make interfacing with the footbed difficult. Second, make sure that that the bootboard covers the entire surface of the boot sole, so that you don't end up having to grind parts of the boot shell plastic that are also effectively part of the surface that interfaces with the bottom of the liner. Make the bootboard a nice thick, flat wedge that sits comfortably and solidly in the bottom of the boot. You could even go the extra step and inscribe lines around the sides of the bootboard that serve as guides for bootboard grinding.