And here's a link to back up all the cons against cohabitating.
http://squamishserpents.ca/care-info...-one-enclosure
You are confusing a thermometer with a thermostat. The difference is one reads temps and one controls temps. Here is what you risk by not having a thermostat and not knowing what the temps are in the enclosure.
(graphic)
http://ball-pythons.net/forums/showt...-me...(graphic)