But you can put pipes to where you want, as you´re not bound to the exhaust rules.
And you can place the exhaust outlet where it is mandated by the rules. What you do with the exhaust below the bodywork is not under control by the FIA.
So in short words I want to do an energy transfer. There is a loss in efficency compard to EBD. But any blown diffusor is better then an unblown imo.