McLaren again started the test with a aero test rig attached to the car. This time the array of pressure taps were affixed to the rear of the car, taking readings from the flow off the trailing edge of the rear wing. Flow Viz paint was also applied to the rear wing endplate to assess the surface around the vents on the upper front section of the endplate
In later tests Button ran the car without the snow plough device fitted under the nose.
Scarbsf1's Blog 
looks like button does all the aero testing
Craig,
What with this being so late in the overall testing schedule, is it something of concern that McLaren is doing this or is it more likely to simply be a matter of fine-tuning CFD models and wind tunnel results?
i.e. Are they not seeing the results they hoped for or are they ensuring the testing ban doesn’t hurt them going forwards?
Could be something related to their simulator parameters??