Bin cage and heat pad?

My set up is 2 sterilite bins without the lids, connected by a 4" pvc pipe. The bins are 66qt each and each measure 20 by 14". I live where it doesn't really rain or snow much, and we're approaching summer and it gets hot! My house really doesn't get cold either, and we always put the heater on if it does get chilly. The breeder that I'm getting my baby from only uses water bottles filled with hot liquid, wrapped inside a sock. She uses a space heater for when its cold, but not all the time. I think I'm going to use heating pads. I'm thinking of using two of these : Amazon.com: MILLIARD Pet Bed Warmer 20"x12": Pet Supplies Amazon.com: MILLIARD Pet Bed Warmer 20"x12": Pet Supplies

My bins are 20 by 14 so this will cover enough area so the hedgie won't feel temperature shock if one side is cooler right? Or should it be a smaller pad? Do I use these all day long, or just at night? How do I use a thermostat/thermometer with this method?

Also, should I use it under the bin on my carper floor, wrapped in fleece? Or should I wrap it in fleece and set it under my fleece liners (which are uhaul pads + fleece)?

Please help!

Attached Images

pre-cage.jpg (88.1 KB)