Saying that it's getting hot in the garage, does this mean as it up to t-stat temp (as that's normal) or it starts overheating?
Have you drawn vacuum on the system to burp it? Have you verified pressure in the system? Do you have any high points that could trap air?
High points in the system was actually an issue we initially had on the GT car. Had several bleed points but now we're getting into race car cooling systems which differ from what you'd want on a toy/street car.
Also for the ducting, watch your cross sectional areas but a good overview on shaping:
http://www.glasairproject.com/GlasairI/ ... stems2.htmI would absolutely have a flat bottom in that nose. I'd seal around the radiator so that you can for the high pressure area in front of the radiator and keep it there. I'd then potentially look into putting slight scoops leading further towards the nose for nostrils you have. This will keep the high pressure in better, and keep it from bleeding out and around the car.
The next big thing is to get air in, you have to get air out. If you have crap flow downstream of the radiator, it isn't going to get good airflow through it.
Do you have any CAD model section views of what you have in the nose of the car?