No, it's not necessary. The contour fan shroud set up covers the entire core on the back side, so it pulls air through the whole thing when the fans are running. The core support only blocks a little over an inch on each side of the core in the front, and even that is still exposed to air, just not directly exposed. I've never had my fans stay on while I was moving faster than 15 mph or so, not even in 110* weather. Heck during the winter I considered making a panel to obscure more of the core like a long haul trucker because I was always running right at the thermostat temp with the fans never coming on.
