diff px in that the lower as in underneath has a lower px and thus air is drawn down to the point if you have a look at small Cessna cowl with out cowl flaps there is a little lip to create even more of a px drop.
next I don't bully anyone let alone your self.
and I can assure you are wrong about a client.
I have also said will not answer technical data I speak in general terms and I have a good reason for doing that.
And as for substance I do that every day with a pen
Cheers