Just a couple of 'hopefully' helpful / interesting stories.

When I went over to Norway in 2004 to feature Stian's blue WRC Escort it had a carbon fibre enclosure around the rad in the boot. Air was drawn in through a scoop underneath the boot floor up through the rad and then out of the tailgate... all enclosed in effect by the carbon surround.

To keep everything looking mega-neat, as Stian always does, he cut some holes and meshed them behind the number plate. First time he let loose up the road at around 100mph I think it was, the carbon enclosure actually shattered into little pieces! Turns out there was masses of air getting in, but not enough getting out and the pressure build up destroyed the enclosure!

Shortly after you'll see in pics that he opted for additional 'outlets' in the boot lid which worked well, certainly well enough for three days abuse at the Gatebil events, but I don't think he was ever quite happy with it.

When the car was rebuilt after the crash, air was taken from the rear-quarter windows through the air-ducts which as far as I can remember was in addition to the scoop in the boot floor.

Then it was rebuilt again for Leif and painted silver but it's still undergoing further tweaks, but at Gatebil a few weeks back it was running without the enclosure and Leif was understandably having cooling issues after around 3 laps of use.

The Rallycross boys have been doing it for years, especially over there and for some reason it seems to always work well in Mk1 and Mk2 Escorts as well but there's certainly more science to it than cutting a hole in the floor and hoping there's enough air coming in and able to get out again!

Good luck with your project though... I might have to do it in the Ka yet as space is very, very tight!