Filler spool holder scale mod

I already had a filler roller printed and working on my Ender Pro 3, when I got it into my head to see if there was a way to build a scale into the spool holder. Turns out, there is!
With a cheap load cell, Arduino nano and a few other cheap components, you can build out an accurate method of estimating how much filament really is remaining on that spool!

https://www.nutsvolts.com/magazine/article/build-a-3d-printer-filament-scale

Not wanting to get rid of my beloved spool roller, I put some effort into modifying the scale designer's components to work with the Filler's slip-lock design, at least insofar as I use it for Ender 3 Pro

Printing:

Full print with 4x4x4 walls/top/bottom and at least 40% triangles infill. Higher percentage and alternate patterns can of course yield different strength characteristics; use your best judgement here.