I love 2ROBOTGUY's spinners, and this is my favorite. But I wanted to be able to put the pennies in the spinner mid-print, so I took his included "Penny Cap", scaled it up a little on the X and Y axes, and a little down on the Z, and slapped it on the top and repeated for the other arms. If you can, tell your slicer to have the printer pause 6 mm up, that is where the top begins printing.
It might not adhere to certain build surfaces well, particularly blue painter's tape, but stick glue solved that for me.
Place a bearing in the center, put the caps in it and super glue them together.