Good thing about naps is they seem to help memory .
Just got up from a nice one and recall taking the back rubber that encases the steel cup in that seal .
I recall not liking the extra 'overhang' and prior to installation used an exacto knife to remove the rubber from the rear edge of the seal cup , right down to the steel . And then a small chamfer on the outside edge .
Didn't look totally pretty until it was seated . That took care of enough material to allow for a just about perfect seat .
Pete .