Thank you Hy -- not just for your helpful response to this issue but for the actual functionality of the internal guider!
Regarding the specific numbers for Proportional Gain:
The user has no business entering the direct pulse-length-per-arcsec value at all! That number MUST MUST MUST be calculated by the calibration and not changed until we recalibrate.
Rather, we should have the option to enter a unitless scaling factor which defaults to leaving the calibration alone. Otherwise we've completely broken the declination calculation that allows calibration to be re-used for different objects at different declinations. If users make any change to the pulse-length-per-arcsec calibration, then the software must untick the "Save and reuse calibration" option in Settings, because the next slew will require a new calibration.
My mount has absolute encoders, so you've discouraged me from GPG guiding. I've noticed my setup produces about 1.5 x as much rms guiding error in DEC than it does in RA, so I'd like to tune the DEC aggressiveness. As it is I get rounder stars unguided for FL below about 1000 mm.
We really need a way to adjust the scaling of our corrections in both RA and DEC that doesn't break the calibration. Something like an "aggressiveness" number from 0% (no corrections) to 100% (full correction), for RA and for DEC that simply modifies the "real" pulse-length calculation that comes from calibration. It could be combined with the "Integral Gain" as you've described, but in my strong opinion it should not have physical units.
Thank you also for the reminder that this is a community project, and that all of us are needed to keep it moving. I am willing to help out with the guiding section of the hand book.