on each of mine the front panels are 3/4 inch taller than the sides and i glued a strip of 1/4 plywood to the front panel ( on the back side of the panel, facing the inside of the hive) of the hive, which gives the bees an extra 1/4 inch of space to move around on the front side of the first comb. if you want to leave them a top entrance you could always glue two short pieces, one on either side, leaving the middle open for the entrance, which would still give the bees that extra space. otherwise they may not center the comb properly on the first bar which coud cause them to mess up every subsequent bar.