It's a very complicated business sorting the cooling and intakes, more so than you'd think.
I'm got a basic 'handle' on it but you really need to read up on the subject.
To sum it up though, all the air that comes in through the inlet should go through the radiator. All the air that comes out should go through the nostril(s). The inlet should be smaller in area than the radiator so that the high speed air diffuses and reduces drag. There are formulas and calculations for inlet area to radiator area and power.
If you don't do it properly you'll, lose cooling, pressurise the clip at speed, increase drag, heat the cabin and reduce downforce/increase lift.
So by all means use the RCR rad, it looks good and will take the power, while ideal to fully shroud and make a nice inlet it would be perfectly acceptable to block up the top section up to the body with some foam on top to have a decent seal against the underside of the body.