I've not seen rear mounted intercoolers before (on rallycross either) but helped with the build of Tom Scarletts series one which had the rad mounted in the boot & this was in a fully sealed section with ducts coming in from the rear quarters, an air vent cut into the boot floor & the escape for the air out of the rear panel. it also had kenlow fans mounted onto the rad but was in need of more powerful fans to be honest but still ran no hotter than most modern cars, & also had a high pressure water pump circulating the water. the main reason for locating this in the boot was to make more room for the turbo but was still just as effective