I don't think you need to worry too much about swarming. I also would not destroy any extra queen cells, the bees will work it out. You should open the box after ten days just to make sure they are each rearing at least one. If the colonies are still mighty after the splits, and they raise multiple cells on more than one frame, I would be tempted to make further splits rather than let their work go to waste :) :) If that does not fit you plan, understand that I'm at the point where I'm thinking more colonies is always better- Haven't hit my critical mass yet :roll: Multiple cells may be left in a split without the consequence of swarming.