Or can only single shims be used? I'm coming from the 'single shim' camp, but with a limited supply of shims, I've wondered about the ability to stack 2 to get a closer balance.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k