old trick from back in the day is inserting a set-screw in each of the 'empty holes'... thus, filling in the gaps.
obviously you don't want the setscrews to be too long and want them to sit subflush to the top mounting surface so that the adjacent ball-stud sit flat as normal..
on another note, i used this back in my Yokomo YR4 and HPI RS4 Pro3 days...
haven't had a single issue with the Tamiya plastics in this regard.