"Why do I want to keep the excluders off? If they build out comb and fill it with nectar I don't want the queen laying eggs in it."
crazy, you are waiting on queens. this time of year with supers of foundation on, you wait until it's drawn, this keeps them busy and helps to avoid swarming, you put an excluder on to foundation before those queens arrive...... and bye bye bees.
like scott said,
" If the queen DOES start to lay in the super, shake the bees down and put the excluder on. They will clean the cells up and fill them with honey after that brood emerges, plus they will have a jump start on drawing the supers. The upper entrance would be a bonus as well so the bees dont have to go through the brood chambers or go through the excluder."
i have had queens lay up in newly drawn foundation in the spring of the year, as soon as she does, the excluder goes on, scott's post. it is better that you have this space for the bees waiting for queens, avoiding swarming, than being too concerned about a queen laying up in one freshly drawn super, until you can divide. hope i made sense?