beatnic:My humi has one of the round, front mounted analogs. It kinda works. I keep a digital inside. But the back is completely open. One, big hole all the way through the box. I was worried that, if the humi did not sit correctly in the hole, then air would be allowed to escape. I took a thin strip of paper and used it as a gasket. I would think that drilling more holes in yours would not be a problem. And make sure the fit is snug on the hydrometer.