One of the issues with these articles we are finding is the air must flow through the mesh whether it is in a clear pipe like the vent hood article or in a rectangular wind tunnel like the dissertation. So because the air cannot go around as the free hole area decreases the drag is going to increase. If you take this to the limit and have a solid sheet your drag will be infinite because no air will pass. In the case of a grill block the air has the option to flow around the obstruction i.e. up and over your car dramatically reducing the drag. If the test setups in either paper had vents in the structure immediately before the mesh that would give the air someplace else to go then we could directly compare.
As for the test setup I do not have a roof rack. I have not come up with a good way to stably mount the meter. A good solid mounting that could be rotated would certainly be useful for testing different angles. Though I am most interested in vertical because that is how the grills on my xB are. Perhaps the handle of the meter could be epoxied into a PVC pipe and at the other end a T with extensions to give leverage for keeping it straight.
That would certainly give me more separation from the vehicle.