2.5 Triumph Spitfire aero' advice plz.

Hi everyone.
Im seeking help and advice regarding the installation of a radiator in the boot area of my project Triumph Spitfire.
Im at the moment fabricating a plug for a new roof.
I realise that this is a contraversal idea, full of pit falls.
Very helpful guy on Triumph forum has highlighted idea of rear diffuser as well.
Not sure if you are familiar with the Spitfire, but basically i have removed a fairly large section, at rear, around the area where rear bumper would have been.
I will not have a boot lid as such. Just a "n" shaped frame. So that area will be completely open, above rear rad'.
The new roof will have three vents, directing air to rear mounted radiator.
So...thinking also it maybe possible to gather air from underneath car....and guide that also?
So... ideas, advice, or anything...would be greatly appreciated. Many thanks.
PS...pics of roof are on blog...
ukcjmspitfire.blogspot.com/  

Is this car a mid engine or a front mounted engine design? If it's front mounted I wouldn't suggest getting air from underneath the car. All that hot air being dispelled from the engine and exhaust will make its way back and hamper the radiators' cooling efficiency. Just a thought that I would throw at you to take into consideration. I'm not too familiar with that model you have and I'm sorry if it dosn't help much.
For mountimg the radiator where you want you may need the expertise of a frabricator and/or body man and/or the advise of some one that know more about the aerodynamics of that particular model so you can see where and how the air goes around the vehicle. It helps to know those things when considering placement of a particular, and essential, part such as that. Sorry I couldn't be of too much help on that but I hope it guided you in some way. Good luck.  

Hi Blackmonkey.
Engine is front mounted.
Thanks for your thoughts...food for thought.
Regards.