Is controlling the temperature precisely as important as getting results that you can reproduce? I use a tempered pre-wash with my drum, and the developer goes in at 94F. I develop for one minute and don't reuse the developer. Sure, there's temperature drift, but it doesn't vary much between processing cycles (assuming non-extreme ambient temperatures) and it averages out to the recommended 92F for this processing time. RA-4 works over a range of temperatures, so it seems like like you have some leeway.