Thought I’d contribute a little to the discussion regarding what I’ve found while playing with the HQ camera for the past couple of days, and from an epi-illumination standpoint. Below is a picture of my setup with an (improved?) illumination arm - it allows for a field aperture to be implemented.
The main issue I’ve found is that without having a significantly long enough tube lens focal length you run into issues with coma aberration.
This image was taken using a lens with a diameter of 20mm and FL of 60mm. (I was trying to avoid vignetting due to the larger image sensor size (useful tool for calculating this for infinity corrected objectives : https://www.edmundoptics.co.uk/knowledge-center/tech-tools/infinite-conjugate-tube-length/).
After some advice, I reduced the tube lens entrance pupil diameter which does help but then you encounter vignetting due to the effect described above. Though the vignetting isn’t the end of the world as I would prefer a fully focused (but not evenly illuminated) field than a poorly focused one, especially as the latter confuses the autofocus algorithms & makes tiling impossible.
Edit: Following image is with 8mm tube lens entrance diameter - can see the improvement but not perfect.
Also demonstration of decently aligned field aperature using my half kohler illumination arm:
