Snow Performance: Home
Subaru guy here. Subarus have had a few different intercooler spray systems from the factory. The one that I thought was the best was the one with a big HDPE plastic tank bolted behind the rear seats in the trunk. It took up very little usable space, held lots of fluid, and kept the weight off of the nose of the car.
I think what the original poster should try is painting the radiator black (if it isn't already black from the factory.)
If he's still got lots of energy and money...then he should step up to Lexus LF-A dual rear radiators. THAT is how it should be done on a car. The 'ghetto' way to do it would be to mount your radiator in the trunk and seal off the whole nose.
Then the problem becomes "How do I get air through the radiator?" You need a way IN and a way OUT. A way OUT is easy; just cut a hole in the rear. The bumper cover is plastic. The trunk is already on hinges. There are a million ways to do that part. The tricky part is how to get the air IN. You could build a huge NACA inlet in the roof ($$$) or make use of the trunk lid or rear wheel wells. My favorite idea would be to build ducts to both rear windows. That way you could open or close the rear windows with your fingertips, thereby feeding or blocking the rear mounted radiator intakes.
Do you think that two NACA ducts behind rear side window glass (in 'standby' mode) would look a bit odd to other cars on the road?