Ah, good idea. Get a smaller size fender washer and enlarge the ID. Could to the same thing with a smaller AN970. Thanks.
EDIT 1: Nope, the smallest AN970 is the -3, at 7/8" OD, so it'll have to be a fender washer.
EDIT 2: It looks like #6 fender washers are 5/8" OD, and available in stainless steel.