Rob,
I would not let the tank go above 80. The tank temp and oxygen levels really worry me. In the wild, the heat does not deterioriate the water and the current keeps refreshing the oxygen. In the tank, the higher temperatures the more chance of oxygen depletion and water quality issues from fecal mater and remains. Roy Caldwell (among others) has mentioned the oxygen problem during acclimation and that keeping the lower end of the temperature spectrum seems to aid in life extension (or keeping the high end speeds up the life cycle). Kenny may be staying closest to where the CO2 leaves the water (allowing for more oxygen). If you have a sump (I have forgotten), you might consider an air pump and air stone even at 80 degrees. Tonmo members have mentioned potential problems with putting too many bubbles in the tank but you can't have too much oxygen from aerating the sump and Roy found that adding aeration to the small chambers for new hatch increased their survival.