I tried these on my early 7200 which is a different set up from your later planter on the closing wheel attachments but the cast hubs I got came with a spacer ring. Is this the spacer you are referring to? I also had to put  a few more opener disk shims behind the hub to get the suggested clearance.

Again perhaps none of this will apply to your mounting set up on the closing wheels but thought I would share.

Ended up taking them off because I could not get an aceptable closed seed trench. Ended up planting that first year with standard rubber tires. Have since went with a pair of the Dawn Curvetines and reduced down pressure closing wheel springs and like them much better.

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