AFAIK, these bearings can be found on AliX in 2 heights. P16 & P16-8. From memory, 1 is 1mm taller than the other. TBH, having built quite a few of these now, i think either works, the slack can be adjusted with the headset cap, spacers, removing materials and so on. shims are easier to add than it is to remove material, obviously.