You might be already aware of this, but latest PHD2 build enables multi star guiding. There is a long thread on cloudy nights
I just wanted to mention it here since I believe it is especially relevant for weight-capable but entry level mounts like the exos2. my experience so far with my exos2 is that it needs to be guided aggressively. I typically have best rms with guiding exposures of 1s, despite picking up a lot of seeing fluctuations. Multi star guiding should allow for a more accurate guiding with very short exposures by averaging out a lot of seeing (three times smaller rms due to seeing with nine guiding stars). Hopefully this new functionality allows to push further the limits of the exos2 for astrophotography.
I will try it this week. Let me know how it works for you,
ES EXOS2-GT PMC-Eight
Starfield 0.8 Field Flattener/Reducer.
ZWO ASI290mm-mini & Orion 50mm Guide Scope
Canon EOS Rebel SL1
SharpCap, APT, PHD2, SiriL, Stellarium