I've used a single valance mount B&B since '95. Only issue I ever had was at the double 50 at the Glen traffic was stopped dead going into Corning, backed up for miles, ~99°F ambient. Solution was to take to the back roads(or stop). I suspect that even a second cooler w/ fan would have been challanged that day.
Even w/ the 3.8RS on 90° days temp stays ~85-90°C
cooler is 5 1/2" X 2 1/4" X 20".
If I were driving in big city type traffic(NNJ?) a second fender mount w/ fan like the Elephant ones would be a big plus.