I have a TOP. I use the Habitat evaporative humidifier with the monitor. I put the humidifier right above the shelves. There is enough room behind the drawers for the air to move. I drilled 1 1\2 holes in the corners on the shelves above and below the drawers and attached 4 fans 2 blow the air up on the right side and 2 blow the air down on the left side. I have perfect humidity throughout. It's been 4 or 5 years now. My humidifier hardly ever comes on. I fill it maybe three times a year at most.
Here is a pic before I moved the humidifier above the shelves and before I added two more fans on the right side blowing the air in the opposite direction. Before that I had the same problem. Hope this helps.......