Before you decide to drill any holes for entrances I think you should read up on managing a long deep hive. Have you considered making/using dividers (follow boards) ? I am guessing you have followed the idea of using 18 or so deep frames – bees generally do well in about 40 litres in volume box (what volume is your complete box?) – thats what they typically look for in a cavity when swarming – but it's not really enough volume to harvest any honey, so the available space often has movable boards/dividers which enable you to manage expansion to around double the volume. There are very often entrances at each end/side to enable other manipulations too. Then after your honey harvest and for the winter you can reduce the space again to keep them cosy.