marion, this is how most of us do it,
the 2 "shim directly on top the 2nd deep hive body, inner cover, then your insulation, then outer cover.
"The problem is, I need a shim above the inner cover so that the outer cover does not obstruct the bees upper exit."
marion do your outer covers fit tight on the inner cover which obstructs the upper entrance?
if it is tight, push it from the back as far forward as you can......sometimes i get outer covers that really annoy me with the tight fit.