Bore a hole in the inner cover near one edge and place some bottlecaps or
pebbles on it to provide some space for air movement.
Inner covers are usually cut to fit a bee escape in an oval hole-I have never
used a bee escape.
Putting the hole near one edge lets you use a baggie feeder without covering
the hole.
An inch or so is fine.
Instead of bottlecaps you can leave the entrance reducer between the covers.
I usually put it near the front so water runs off the top at the back.