i run a fan, all year long. it's at the ceiling height,helps to even out temps and humidity.
a few questions, what are the room temps, what is the room humidity? i personally wouldn't want a fan running air inside the setup, too drafty. if the tub is a tall one, you might want to do 2 rows of holes. i space my 1/4" holes about an inch apart. for tall tubs one row down low and one row up high might work better.
vaughn