How do I get these little washers off of the panhead screws?

I bought new star washers for the handful of panhead screws that were missing them but I cannot get these little extremely thin washers off. And the washers have a slit in them but they are not lock washers.

Should I just leave them alone and install the star washer on top of them? Since these are such short screws I hate to take away even one thread of bite.

I've tried prying them with a screwdriver, putting them and trying to unscrew them but they won't unscrew on the threads. They're almost like captive washers.
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1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)