Genghis
I have been trying to calibrate the pitot-static on our RV4. I looked at the two methods that you describe but finally settled on a method described by Doug Gray in a paper 'Using GPS to accurately establish True Airspeed (TAS)' of 1998 that is widely available on the internet.
In this you fly any 3 headings and his supplied spreadsheet equations will calculate the TAS. It was quite easy and the results are in the area I expected from observed wind, estimate of speed. But to be sure as a calibration I need to understand the derivation of the equations and this has got me beaten. Are you familiar with the method ?