[aerohead]

I've yet to be able to predict what one might gain from any particular mod.
Kamm and Fachsenfeld,with a 1/10-scale model of a 'car' with about the same amount of aft-body as the Integra; going from a Jaray,to Kamm tail end,saw Cd 0.33 got to Cd 0.25.You might consider this a best-case-scenario.
Worst case would be zero-gain,as MetroMPG saw on a CIVIC project if I remember correctly.