Add PIERSIDE Keyword To FITS Header

Analysis/reduction software sometimes needs to know, for German Equatorial Mounts, whether images are taken looking to the East or to the West as that will have the effect of potentially inverting the image. The keyword that I need is PIERSIDE as documented by Diffraction Limited (and probably others). Maxim DL writes it to the header. Can you add it into the header in SGP?

On a related note, I see the FLIPPED keyword but it always seems to be false. How does that get set?