I would just put it anywhere on the cool side.

In my opinion the only downside to using a tub is the issue you're facing right now, maintaining ambient / cool end temperatures.

Rather than heating your whole house to 74, you could put the snake in one of the smaller rooms, and buy an oil filled radiator, and put that on its own thermostat. That way you could keep the rest of your house cooler and still keep the room that the snake is in warm. (unless this is something that you've already done)