Underbody aero - specifically diffuser

[alj]

Hi all,

This is my first post, but I have been reading your wisdoms for an age. You guys and Katz and McBeath have taught me heaps about aero. I have designed my own aerodynamics for a GT racer from you. Now I wish to enhance the underbody, specifically the diffuser.

I want to introduce twin outlets from the exhaust, from what I have read 13 degrees is the sweet spot for aero. I was thinking single tunnel diffuser with the rear wheel disturbance separated from the diffuser air. Though I am not locked to this design, also I have no idea where to place the exhaust for best effect.

I have attached a crude drawing (apologies). I would love your guys inputs.

http://i182.photobucket.com/albums/x149 ... egrees.jpg