Update 2022-12-05: Added V2 which is more of a slotted opening tapered to the left and right to account for times when you print something very tall. It gives more flexibility for the filament when the print head is farther away from center.
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Print 100% infill with fins facing up.
No supports necessary.
Install by unscrewing stock spool holder arm, placing this underneath (with fins facing down towards build plate), then screwing the arm back down on top of it.
The author remixed this model.