Marc,
Of course, Imirie Shims are a total violation of Bee Space, and  THAT is the
exact reason that they should ONLY BE USED DURING A NECTAR FLOW AND WITH
DRAWN FRAMES - never with foundation!

Many beekeepers UNDER super resulting in the bees building BURR comb or
swarming
for lack of storage space for thin waterery nectar.

Most bee researchers and almost all professional honey producers install
their supers of DRAWN COMB all at one time rather than one now, another in a
couple of  weeks, followed by a third, etc.

If an Imirie Shim gets BURR comb in it, you are either using foundation or
there are not enough supers in place.  I started using shims over 40 years
ago, and rarely have any burr comb built in them.

You say that you use shims for "other" purposes.  WHAT?

You say you use upper entrances during a nectar flow.  An upper entrance is
FAR MORE important in the winter than in the summer.  You want to get rid of
that DAMP
air from exhaled bee breath during the winter.  Cold does NOT kill bees, but
DAMPNESS does.

I don't like auger holes in my supers for two reasons: They making robbing
too easy; and I always accidentally put my hand or wrist right over the auger
hole and get stung.

On April 15th, I install 5 medium depth supers of drawn comb on each colony
arranged in the following way:
queen excluder, Super #1, Imirie shim, Supers #2 & #3, Imirie shim, Supers #4
& #5, Upper Entrance cut in front edge of Inner Cover (that is open 365 days
of the year).

Indiana should have weather very similar to Maryland, except you have a lot
more farming than I do.  My TOTAL nectar flow is OVER by June 15th, and ALL
of my honey is made quickly, from April 15th to May 31st (sometimes extending
to June 15th).

I hope that I have helped.

George Imirie