This is interesting and will be good to see some figures.
I've just bought a dual cone Green Filter with a 45 degree alloy pipe and 80mm joiner.
I'm going to be removing my battery and having a second head light for a straighter flow for induction for the track.
The set up I'm buying is a good bit more expensive then the above but would doubt there is much flow difference.
If Jetex did a dual cone I would have gone that way as there cheaper.
The reason I want the dual cone is I'll direct this toward the front of the car and have other supplies to the sides of it from the OEM grill.
Nice one Jonnyjonjon for doing some investigation into other products, we need more people on SCN doing this.