Machdiamond
the small static ports few meters upstream of the cone measure the absolute static pressure at flying altitude, so I cannot understand the need to calibrate through tower fly-by, probably it was the aircraft static ports which were calibrated and compared to cone static port pressure.
However, for stall tests, in order to appreciate the difference between the pitot tube pressure indication and the 'true' static pressure measured 50 meters behind the aircraft, with its lag in reading due to the length of the small pipe, we used to calibrate the two systems recording the two pressure peaks resulting from exploding a toy balloon in close proximity to the two pressure sources (pitot and cone static pressure ports)
Regards
D.