I am building a rack system that will house 4, 28 QT tubs for my 4 BP's. I plan to switch out two of the tubs for 41 QT in the future when my females are larger. The rack will be short and long as apposed to tall and deep and placed in my room that is generally on the cool side from 65-70. I live in an old house so keeping ambient temps consistent it almost impossible. So what I am wondering is what width of heat tape should I get? Currently I can't decide between 6" and 3" THG tape. Additionally, I have seen people place the heat tape on one end of each tub, in the middle of the long side of 28QT tubs, and underneath one end of the tubs. What I want to know is which placement and size would work best for maintaining temps for 28 and 41 QT tubs while still providing a gradient.