I am making my incubator today...I bought a new Styrofoam cooler at walmart it's walls are about 1" thick. I had another one from steaks, but I was hoping it would be bigger. It's not. They are almost identical inside size, but the meat one has 2" thick walls. It's not pristine condition, but not anything which would hurt performance. Which should I use? Does the wall thickness make a big difference on maintaining temp or can i just use the new clean one?