Hi there
The resistance you feel when tightening is the posts seating in to the chassis, perfect fit.! The grub screws just hold them in and carry no load as the post seats do that job. But If you have a problem then your idea sounds fiesable . But remember that the grub is steel an the chassis is Ali (softer) so the drill may try to wonder sideways! Only advise I can give is use a pillar drill and keep the bit short in the chuck
Good luck!
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