Soo it's been a few weeks. I've been reading quite a bit. Looks like a 30F swing is sufficient for all UHLers and that it's the drop not the temperature that is significant. Additionally, a UHL grow chamber is not needed for young plants. I have one so I intend to use it to figure out what works.
During all the research and trials, I flipped the spectrum to blue-white at 53.3µmol/s and expertly scorched all the tips on the HI sphagnum. I have been propogating it from an orchid stowaway for the past year.
I removed half the sphag and placed back where it was happiest and the rest on the bottom of the chamber. I flipped the spectrum to red-white at 44.9µmol/s
Also, for some reason my temps where out of spec low. So I moved the band up because I was getting subzero indications on the sensor. I also set up the fan to blow straight onto the sphagnum in the bottom of the freezer. As a result, humidity quickly picks up when below the setpoint. The temp rise is solely the LED light fixture's contribution over ambient temperature and seems to plateau around 75F. Fan only really kicks on during the cool-down as the humidity plummets. You can see the cycles during the night.
Concerns going forward are:
Is my light too close? It's 8-Inch from the plants crown. I have lids drying up, but it could just be shock from shipping. I never refilled the pitchers.
Is my humidity too high? It's seems fine, but it literally rains every day from the condensation on the cover.
Should I sacrifice humidity stability for increased airflow by turning to airflow back onto the plants? Maybe add a constant fan to run during lights-on.
I don't want to shift too many things at once, but I'll write my observations as conditions change.