I RUN A 4" AND AM VERY HAPPY WITH IT. MY FLOWER ROOM IS 5' x 4' x 6'.

I JUST BOUGHT A 12' VORTEX,,, OMG!!!! IF IT HAD WINGS, IT WOULD FRIGGING TAKE OFF. I HAD TO INSTALL A REO-STAT SO I COULD CONTROL THE AIR MOVEMENT. MUCH BETTER NOW.

BUT TO ANSWER THE QUESTION, THE 6" SHOULD BE FINE. INSTALL A REO-STAT IN NEED BE, TO SLOW IT DOWN.

GOOD LUCK