Hello Mark,
Regarding my Imirie Shims:  You indicate that the shims have been in place
for over 2 months.  WHY?  I may be wrong, but I am not aware of any strong
nectar flow
taking place in late February - early March.

Bees do NOT use holes drilled in supers, staggered placement of supers,
broken super corners, or Imirie Shims as ENTRANCES and/or EXITS at any time
other than very warm weather with a strong nectar flow.

You are right about one thing: they have to "learn to use" entrances other
than the standard bottom board entrance, but as soon as a forager age bee
finds an entrance directly into the super area, bypassing the crowd in the
lower brood area, that is the entrance she will use.

I hope I have helped.  Thanks for using my shims - I have been using them on
over 100 colonies for over 40 years.

George Imirie
Certified EAS Master Beekeeper
Starting my 70th year of beekeeping in Maryland
Author of George's PINK PAGES