Pirelli: 2017 cars won't be 5 secs faster, because physics

You might have heard of the promised "5 sec time increase" that new regulations are supposed to bring to F1 in 2017. Adrian Newey has already claimed that this isn't possible, and now Pirelli have pointed out that the current plan to increase the size of the tyres won't mean faster lap times either (surprise!):

It said pressures would have to be as high as 27psi - about 50% higher than would be considered by teams to be 'normal'.
But higher tyre pressure reduces grip, which would mean diminishing returns from the increase in car performance.
The other problem was that with reduced tyre grip, a greater proportion of the lap-time gain would come from aerodynamics, and the feeling among engineers and world governing body the FIA was that this would make close racing and overtaking even more difficult than it already is.

Turns out that improving F1 is a pretty tough nut to crack. Can we just start looking at the aero underneath the car and doing whatever it takes to bring the cars closer. Please? 

Source: BBC F1