I am reusing my mating nucs on 8 frame equipment over the winter. I purposely made them to hold 3 frames with a follower board in the Spring--however can squeeze in a 4th frame if needed. I have the boxes doubled up (side by side) and stacked on a divided solid bottom board. They have been treated for mites and have been fed. Winters have been pretty unpredictable in Richmond, VA the last few years, so I am making some feeding shims for emergency food. My question has to do with using a queen excluder below the feeding shim. Using one will eliminate the possibility of the queen crossing over--but is it absolutely necessary?