Entrance size for Top Bar Hive

[slturner55555]

Hi. I am very new to bees. We bought a Top Bar kit which had holes on the side. I would prefer an entrance at one end. I was thinking of making a slot near the top of the hive. I was think of 1/2 inch by 4 inches wide. My question do you think this is big eough? How far down from the first top bar should the hole be.
Thanks
Sandra