Spool guide to prevent spool being pulled off cradle

The taller spool cradle design has the downside that the spool sides are not constrained by the edges of the cradle. This is due to the larger diameter BB ball bearings being used.
I designed this little widget to clip into the holes on the cradle that provides a guide for the cradle and (in my case at least) prevents the spool from slipping off the cradle.

I also modified the ball bearings themselves to add a groove to them for extra stability.