I have a CHE on a large tub hooked up to a Herpstat 2 thermostat. Never had any problems with it and my snake enjoys the extra space. Here is the tutorial I followed on the correct and safe way to do it. For a tub as large as yours you may need two CHEs, which means you will also need two thermostats or a thermostat with more than one output.

No matter what type of enclosure you use, you MUST have a thermostat hooked up to every heat source. This is the single most important piece of equipment in snake keeping as it can mean the difference between life and death for your snake in a matter of hours. I would highly recommend getting a Herpstat or Vivarium Electronics thermostat as they are the industry gold standard, the most reliable and long-lasting, and equipped with safety features to prevent electronic failures that might result in your enclosure overheating and killing your snake.

The only downside is that these thermostats are pretty pricey, but they are worth saving up for IMO. A Jumpstart thermostat is a decent cheaper option but beware as they can fail after a year or two and do not have safety features.