So I remade this because it works well, and the bearing holes weren't the right size and I wanted a way to clamp down on the tubing. Place some supports under the clamping part.

https://youtu.be/MwEhKZO7G10

I printed mine with super dry taulman bridge nylon, 3 walls, 4 bottom layers, 5 top layers onto watered down 3d eez on a build plate @ 90C, print temperature 288C.

Reference original design for BOM.

I also added some precision shims (openbuilds) but washers should also work well - the point is to clamp down on the bearings so they are stable.

The bolt used is a 5mmx15mm - with a lock nut.

also included are cad files for folks use out there.