I know what the maunal says for the SERG, and I am not happy with that setting. Seems harsh on a big bump and has thrown me out of the seat more than once, same bump on my Fatboy and I do not come out of the seat.
What do you run in yours, what the manual says or more or less?
The really important part is to not exceed the maximum pressure listed in the manual, and that maximum is different for the standard length shocks and for the "lowered" shocks. Other than that, just start with the pressure the manual recommends for the weight you are carrying and adjust to fit your preferences from there. There is no absolute correct number, it will vary.
BTW, you may find the same thing that those of us with SEEG's found with the lowered shocks. People tried using lower pressures to improve the harsh ride and found that it got worse. That was because the shocks were bottoming on a regular basis and actually needed
more air pressure to keep them from bottoming. So you may want to try
increasing the pressure, but no more than the max listed for your bike. Use the same stretch of road and try increasing the pressure 5 psi, then decreasing it 5 psi from the recommended pressure. This should tell you which way you really need to go.
Jerry