Back in it, but new house.

[Bogertophis]

Yeah, I've got thoughts, but first I have questions. What heat element (flexwatt, heat cable) are you using to supply back heat? What do you mean by "doubling up"? Are you trying to regulate two elements with one thermostat or are you using two? What are your current hot and cold side temps? How are you measuring them? Armiyana's experience not withstanding, keeping ball pythons in a rack in a cold basement sounds like a bad idea.

I was thinking that the "doubling up" merely meant using two heat sources (tapes or cables) to effect the proper temperatures, & that sounds like a winner to me- as long as they're properly regulated (& as long as the entire tubs are not heated- the space at the front still offers them the cooler temperatures they need for thermoregulation). It's no different that what many others do. In general, it's going to take something like this for a chilly basement to be suitable for snakes that need more warmth, the way BPs do.

There's always some risk of malfunctions, but diligence is always a good idea for snake enclosures anyway, with accurate temperature readings a must. The warmer they need to be, the greater the risk. OP- Just be sure to re-check the temperatures & set the whole thing up to test it for a week, preferably, before any snakes occupy it- it can take a while for temperatures* to stabilize. (*they tend to increase as all surrounding materials gradually warm up- initial temperatures will not be accurate) Also keep checking if seasonal differences change the ambient warmth in the room- you might need to adjust for seasons.

Armyiana brings up a good point though- about heat rising in a rack system (potentially making either the bottom ones too cool, or the tops ones too warm). I have never used any sort of rack of tubs for snakes- again, you'll need to test all this out before snakes move in. You don't want them too cool & regurgitating in the lower part of the rack, or the ones at the top getting neurological damage from excessive heat. Every set up is a little different (some materials hold warmth better than others)- so your results may not equal the results that others get from their set-ups. Test test test...