Getting the temperature right when using MHP isn't a big problem, but you do need to know that the temperature can be increased inside the cave significantly if the ambient temp is also very warm.
Before getting my most recent batch of chicks this past May, I set up the pad and frame and tested it, even though I've brooded this way twice before. What I discovered was the temp inside the cave read over 100F when I tested it on my work bench in my warm garage. When I tested the exact same set-up outside in the run where it was much cooler, the temp inside the cave was 80-85F.
So on warm days, I lowered the setting on the pad for the chicks. If it's too warm inside the cave, they are less likely to use it and benefit from it, so it's important to adjust the setting as the ambient temps warrant.
And keep in mind it's direct contact with the underside of the heating pad that makes this concept work so well. It's very important to adjust the height of the frame each week as the chicks grow so that they will fit comfortably.