I no longer do "pretty picture" imaging....
For the spectroscope I have to hold the star image on a entrance slit 20 micron wide for as long as possible. Usually a hour or more exposure is required.
The seeing disk ie FWHM 3sec must remain centred on the slit for maximum efficiency. I use a beamsplitter guider/ Lodestar/ PHD and Al's reticule - so I'm guiding on the target star image at 2750mm focal length.
I'd don't worry too much about PHD - it can guide on the image and keep it centred - the guiding must be much better than 0.5 x FWHM (or I'd start to see a drop off in the light intensity)
For proper sampling (Nyquist) the image should cover at least 2-3 pixel, therefore your unbinned sec/pixel would be good for a seeing of 3 arc sec.
Looking at the SBIG data:
https://www.sbig.com/products/cameras/stf/stf-8300m/
That's one hellava camera!!!!
How do you intend guiding? OAG?
Also, I use the C11/ spectroscope on a NEQ6pro mount....never measured (why?) the PE etc - all I know is that with proper polar alignment and good balancing it just does it's job - PHD locks on and holds that star image on the entrance slit......what more would you want?
I'm sure some of the active imaging members may give their opinions....