Is he still squeaking when he breathes?

Even if he isn't, you might want to raise the warm and cool side a few degrees each. I don't know if you live in a cold climate, but keeping the enclosure next to a window can expose it to drafts.

Also, you say that the morning sun warms the tank a couple of degrees...Temperature swings can be stressful to bp's, even if it is only a couple of degrees. That's why most people will recommend a proportional t-stat as opposed to an on/off one.