Remix of https://www.thingiverse.com/thing:1077430 with a few changes.

• Optimized code a bit.
• Enabled changing the size of the center hole to allow attaching to a drill or other shaft.
• Added option to make the center hub spoked instead of solid.
• Fixed the cylinder of the bottom half so that it extends to the top of the top half.
• Added suggestion by TuxSoft to create large windowed cutouts in the spool.

Unfortunately, the online customizer does not support the libraries used for the cutouts, so you must download the scad file and open it in OpenSCAD. The customizer in OpenSCAD works fine.

I don't actually suggest using the windowed version for braided fishing line, as it will bulge out of the sides. I do suggest gluing the halves together with CA glue. During assembly, you can choose whether to have the slots on both halves aligned or offset by rotating one half 180 degrees.