I calculated the response when moving a QPD from the beam profile measurement posted in klog16608.
Attached figures are the result for PIT and YAW.
Calculated slops are 3.1 cnt/mm and 3.0 cnt/mm for PIT and YAW, respectively.
These results are 10% larger but seems to be well estimated.

Details of calculation:
I assumed that the beam is gaussian beam and beam diameters for PIT and YAW axes are measured ones (1.017 for PIT and 1.055 for YAW).
I take into account the slit between each segment and segment size for calculation (slit size is 30um and QPD size is 3 mm for each segment).
I also take into account an ambient light as an offset for normalization.
Since QPD sum when beam doesn't hit the QPD is roughly 120 counts and when beam hits is 4900 counts, I calculated {(seg left - seg right)*(4900-120)/4900}/{(seg left + seg right)*(4900-120)/4900+120/4900} for YAW, for example.