I've done a lot of imaging with the uncooled QHY5III-178C. I also have the cooled ZWO ASI178MM. In terms of the 1.25" form factor, you don't have to use it that way since you can mount a short T-thread to C-thread adapter to the nose of the camera. I've used it that way down to f/4.2 on my Tele Vue NP127is and have never noticed any vignetting (and I don't even use flats). In fact, I never mount it in a 1.25" eyepiece holder. You can find lots of images here on CN that I've done with the QHY, both DSO and planetary. I suspect that I was one of the early adapters of that camera, starting about three years ago with sample images here on CN from that time up until just recently -- so several years of continuous use.
Here is a link to my "first light" report on the QHY5III-178C that I did in June 2016 (includes early images, with links):
And, below is an image showing the QHY5II-178C with the T-thread to C-thread adapter mounted to a Baader MPCC coma corrector (most of the tubes and adapters are there just to get the required backfocus for the coma corrector).
Edited by james7ca, 24 April 2019 - 12:13 AM.