Out of bounds temps tend make certain dev ingredients behave differently in relation to other ingredients than they were intended to do around std room temp of 20C. This affects not only contrast but final image color, and esp how the different emulsions in a VC paper might come out relative to one another. Can't you set up a cooler water jacket around the dev tray, containing a cold water drip line or Blue Ice pack? Don't confuse RC specs potentially related to automated roller transport processors with how fiber based paper is going to perform in an ordinary tray.