On the subject of holes in supers for upper entrances:
 
Yes, they work, but you have to remember they're there when you are working
the hive (otherwise you will get a hand full of stings).   Also, you have to
remember to cover them when boxes are in storage, or you will get wax moths,
mice, and possibly other non-bee things.
 
Imirie Shims avoid these problems, but they do represent another piece of
equipment to fabricate and store.
 
If you like holes in hive bodies, then use them.
 
ps.   Another great way to make a supplemental hive entrance is to cut a
notch in the inner cover.   This upper entrance becomes a permanent part of
the hive, and the bees love them all year long.   Improves ventilation too.
 All my inner covers are so notched.
 
W. G. Miller
Gaithersburg, MD