i had trouble with printing this in pla and the spool snapping at the string holding point, so i modified it to have a smaller opening and rotated it 90 degrees, i'm about to test print it shortly.
update, having printed it, i have found that the hole comes out fine, but was too small for my string, it may work on various threads or smaller strings, however it is still much more durable and simply taping/superglue-ing the string on has worked wonderfully