Summary

I love the original but I didn't have a ton of room behind my printer. And I wanted to print it in smaller parts.
So I just made it so the main rod can slide in to the mounting piece.
That also gives me the ability to switch out spools quickly, instead of having to twist and tilt that piece out of the back of the printer...

By the way, the normal infill setting is fine with this, using ABS, it is plenty strong enough ;-D

From the original design, by @nas7,

This is a Universal FlashForge creator pro spool holder designed for the models that have a slot where the holder clamps. This design should fit any spool size and diameter. The closing mechanism is based on a cone, where the spool rests, pushing it downwards and locking it into place using slots. The closing cone piece will rotate but won't be able to exit the holder until an upward force is exerted. This is my second version and it works flawlessly. The diameter of the spool holder is 19 mm and the length is 110 mm. The closing cone larger diameter is 56 mm. All my spools fit with these dimensions, even the new Octave 3DP very small spool hole of 20 mm.

This FF spool holder was inspired by two creations: Thing 714533 by davedfx and Thing 508896 by CreativeTools. I didn't want to use metal screws like other designs, so I redesigned a holder with slots with a larger cone that due to the weight of the spool will lock into place but it is free to rotate (instead of using a threaded design which will not work for this application).

Please check it and let me know if it works for you.

UPDATE: added an optional washer for large diameter spools, so that the internal washer cone also rotates minimizing the friction (this washer enters the spool holder before the filament spool). This is an additional part that doesn't change the previous design.

UPDATE 2: added a new second closing cone with a larger end diameter to accommodate spools with diameters up to 60 mm. The new external larger end diameter of this cone is 67 mm.