Introduction
I was able to reduce the rolling friction on the Siraya Tech carboard spool with this plastic insert. I found it helped a lot with printing flexible filaments that easily under extrude from feed path friction.
As pointed out by @RichHayman_2523450, it also cuts back on the dust made by the filament mount rubbing on the cardboard roll.
Customization
You can scale the insert to fit holes of other diameters. A planar scale (2D) is preferable. To find the scale factor solve:
ScaleFactor = TargetDiameterInInches / 2.190
Printing
I recommend printing in PLA because of its low friction.
Prints without supports.
Use
Press an insert into each side of the filament roll before loading the spool onto your machine. The insert will gently clip into place. It can be pushed back out later and reused.
If printed in PLA, remove from spool before drying.
The author marked this model as their own original creation.