I'm guiding with an ASI OAG-L (nice big prism) and have pretty bad vignetting on my guide frames. Sometimes this causes trouble for SEP multistar guiding.
Is it possible to set up the guider with a master flat shot through the guide camera?
My kit: SW 130PDS on a HEQ5 Pro mount, ZWO ASI533mc Pro, 30mm guidescope with ASI120mm mini, managed using Kstars/Ekos, RPi with Stellarmate OS, ASI224mc, bits and bobs for visual observations.
Depending on the target and the surrounding star field yes I have tried loads of different settings in the guide module.
Multistar is usually best, and a bigger guide field helps a lot. It would be great to use a flat to adjust the illumination, but I guess Ekos has no facility for this.