Karen,
You mentioned using IMIRIE shims, but they got messed up with comb.  You
further
mentioned that you are using foundation.

As stated IN BIG BOLD PRINT in all my writings, you cannot use my IMIRIE
shims with foundation because the bees will just build burr comb inside the
shim.  You must use DRAWN COMB when using IMIRIE shims, and then the bees
will never build
burr comb inside the shim, UNLESS there are not enough supers of drawn comb
in place.

I hope I have helped.

George Imirie in my 69th year of beekeeping in Maryland
EAS MASTER BEEKEEPER
Author of George's PINK PAGES