I'm really liking this project.
It may be worth rotating the PSU around to pull in air from the front through a *vent. I had the same layout as you in my ncase with an open GPU and the PSU got pretty toasty with the fan running at full tilt.
I've looked through your builds and see you've discussed it but can't seem to find a picture of it. Any improvements on temperatures, did it move a decent amount of (warm) air? Push or pull?