Thanks for designing this and sharing it! I had just finished putting my Prusa MK2 together and was ready to print when I saw the "flaky" way they held the spool. I guess it probably worked but I was afraid the spool might fall and damage the bed.
I also have a Lulzbot TAZ5 printer so I printed this out. I printed at 20% fill since this was just a "test". I found the diameter too small for the Gizmo Dorks filament reels I mostly use. So, I scaled your design up to 110%. It could probably be scaled up more, but, I was afraid I'd then have trouble getting it out of the reel. Also, I found that at 20% infill, the "fingers" broke off quite easily. So, for the final prints I just set the infill to 100%.
I think I may still look for, or design, a spool holder that uses some kind of "through" rod to make changing spools even easily. But, for now, your design enabled me to safely get started with the Prusa!