If the probability of rolling each of the individual results on a given die is influenced by the weight of material removed from each face to create the specific pips or numbers that face has, why not:
a) cut seven pips in each face to a three-by-three grid then ink only those pips actually needed, or
b) cut the pips or numbers on different faces to different depths, i.e. cut the one six times deeper than the six, to equalise the weight of each face?
_