I've return more than one new set of slicks due to them taking more than eight ounces to balance them.
I have seen a bunch of slicks that were out of round as well as having severe heavy spots on them
I was told by one of the west coast racing tire reps that those problems are usually cause by the factory workers taking them out of the molds to soon and letting them set on the tread part of slick making them become mess up like they are, out of round and a bad heavy spot
IHTHs