The temp guns measure surface heat. You'll need an Accurite or something else to keep track of the ambient temp. IMO, the surface temps are more important, cause that's where your BP is. If your surface temps are good, the ambient usually will take care of it's self....especially in a tub set-up.

As for holes in the tubs, I have 7 holes in the front of the tubs, placed 3/4 of the way DOWN the tub, and 7 holes in the back of the tubs, placed 3/4 of the way UP the tub...heat rises, and I feel this promotes air flow. I also have 3 holes placed high on each of the long sides of the tubs...not sure they are really nessisary, but they work for my set-up.

If possible, experiment with the number of holes till you get a balance between heat and humidity.