Universal Quick Clamp/Release Filament Spool Holder For 8mm Bar

I got fed up with reel slap putting ripples in my printed parts, so wanted some spool centres that'd fit the 8mm smooth bar on my G2S.
Unfortunately, research suggested that everyone has got different spool sizes, so I needed to make something that would fit broadly, and considerably more than the claimed "standard 50-56mm" that I found variously online.

In addition, I wanted it to rotate reasonably smoothly, and be quick to add and remove without messing around with screw-threads and so on.

As such, this setup can be centred and clamped onto the spool one-handed, and fits spools of any width (depends on the length of your 8mm bar, and how heavy the spool is, though my 1kg ones I'm testing with are fine).
The main body fits spool holes of 74-50mm, and if you've smaller than that you can clip in the extension, which even fits the stupid 25mm holes on my Robox reels.

For a pair of mounts you'll need:
2 608 bearings
2 M3 nuts
2 M3x12 screws
And 2 each of the "Base" "Cam Lock", and "Clamp Mount" prints.

The "Small Spool Extension" is optional, as mentioned above, and just clips onto the mount.
The "Anvil" is also optional, for where you've got a solid face on one side of the bar and don't want/need to clamp it specifically; the Anvil replaces the Clamp Mount (and Cam Lock) and just clips on and allows you to apply force through the spool to your solid surface.

This was designed for solid 8mm bar; it may work on threaded 8mm, but you may need to scale the Cam Lock in xy by a percent or two for a reliable clamp.