If you're designing your own keyboard like I did, I used footprints from marbastlib in KiCAD. These include holes for the PCB on edge.cuts, and plate cuts on user.eco2. Double check that you have centered them properly. They can snap 1mm too low by accident.

However, it does not include footprints for the 3u stabilizer. From my testing the width of the 3u bar is 40mm if you want to make your own. (For clarity on what I mean, this measurement for the 2u and 6.25u bar are 24mm and 76mm respectively.)
Of course, best is to just measure for yourself rather than trusting a single reviewer.

The one star deducted is for this page not having any information on the 3u stabilizer, which got me into some trouble as well.
Lastly, if posting links in reviews is allowed, here is a higher res version of the datasheet: https://ae01.alicdn.com/kf/HTB1uuM3cqSs3KVjSZPiq6AsiVXaH.jpg

Kailh 1350 Choc Switch 6.25u Stabilizer Set