The dragging depends not only on spool. Check the wheels and also the hexes on shafts. they are a little bit smaller then usual wheels and have additional movement.
The spool is not the best one, but you can recheck and fill it a little. Also you should check the tightening spacers, they are black and it's hard to see if they are all right.
that part seems to be for the front, I ordered one to try. will see.