If you have more than 6 switches (breakers) in the subpanel in the shop,
it
needs to have a main disconnect. If it has six or fewer switches, you can
get by without a main disconnect.

Can you document that? My subpanel has room for 16 breakers (I am using 7
of them) but nowhere for a main disconnect.
I don't know why you would even want a main disconnect; doesn't the breaker
in main panel do that?