Question about the cool side of the enclosure...

If the cool side of my enclosure stays around 69-70 degrees on the main level (I have four levels), should I run a uth mat with a thermostat set around 72-75 on the cool side to keep the cool side warm enough?
I do use basking lamps and my second, third, and fourth levels are all where they should be (within normal limits) but I could never get my main level cool side any higher than 70 degrees. Several people in the past told me this was ok but I'm finding that after four years a lot of the things I thought I knew were wrong...
I'm currently running two uth mats on the warm side and my levels are great 87-88 inside the hide (temps checked regularly) and 83 degrees on top of the substrate (temps checked regularly) where there isn't a hide. The cool side is staying at a constant 69-70 degrees but Markey has been burrowing under the substrate on that side (she has always preferred cooler temps) and I'm sure it's cooler underneath....
Thanks!