You would only use shims that would lift the shaft upward if you cannot obtain a proper wipe pattern with the roller over the valve stem by using the rocker adjuster and pushrod. Or in a case where the spring retainer interferes with the rocker.
I don't know what head he's using but with a traditional Mopar shaft mount rocker arm system the adjuster and push rod length have nothing to do with roller sweep on the valve tip. Once you have the rocker arms the only thing that will affect where the roller sweeps is moving the shaft.
