Made the diameter of the center narrower to accommodate tightly wound filament samples. I have printed about 10 of them so far using samples I need to use up and they work great. Unlike the original there is no place to hook the end of the sample in the center of the spool but since I'm relying on the runout sensor this is good so the filament can't get stuck to the spool when trying to use every last centimeter. 

Big thanks to @Lopatka_921 for the original great design.