I 3D printed a little centering collar, so I could get the center of the hole in the bracket.
I say "mostly" because the right-angle drive couldn't take the torque, even though I was going slow and putting only light pressure on the bit. It ejected a circlip while I was using it, and became useless. I did fix it once, but it immediately broke again.
I literally finished this hole by turning the step drill with a ratchet.
Tomorrow, I'll be hooking up the accelerator cable, and then looking for next steps.