If you think the temperature-issue with Rodinal needs closer inspection develope a foot or so at 18C and another one at 24C. You can judge by yourself if you find a difference, provided you look at equally dense parts.

BTW: If your developing times aren't too long you can mix developer at the right temperature from a gallon of tap water stored in a fridge and use the rest to keep the tank cool as needed. Just put a thermometer into the tank between inversion cycles and watch where the temperature is going.