I don't think this was brought up before, but for those who want to use Costar stabilizers..
Black stabilizer clips fit perfectly in the plate's skinny parts of the holes. However, I had an extremely tough time fitting the white stabilizer inserts into the clips, and even when I did, keypresses didn't work, because the insert didn't fit through the clip on the travel back up.
This is why I've avoided using Costar stabilizers with these plates for so long. But I've just been unsatisfied with how the Cherry stabilizers felt with the spacebar, so I figured out a solution today. With the black clips already mounted to the plate, I took a pair of pliers and pulled the vertical sides of the clip (moreso the back) outwards, until I got the white inserts to sit inside the clip without touching those vertical sides.
Loving it now - Costar for the spacebar and Cherry for everything else.