Already using a custom curve, which is set a lot more aggressive than MSI's stock curve. I actually disassembled my card and reapplied a better thermal paste as well; this gave me a noticeable drop in temperatures.
I did a fair amount of testing and found that my card runs rather hot if left at stock settings, so much so that it throttles itself way before the power limit is hit (at stock settings, I almost never saw 1.9 ghz, while max clocks are actually set at 2.1 ghz).
That's why I was wondering if Dark_Skye's undervolt was conservative enough, because reading online guides, 850mv/1875 seems to be the range that most people would go to for an initial undervolt, which to be fair, is a good point to start with, unless the airflow of the case used is not great. In practice, I found that even at 850mv/1875 mhz, there was no difference in temperature compared to stock settings (about 80 degrees); in a poorly ventilated case, the card is no where close to touching the 100% power limit. Only when I hit about 825mv/1845mhz, there was maybe a 3-4 degree improvement.
In the end, I settled with an undervolt of 800mv/1815mhz, because I preferred a lower power draw and fan noise, and also because my own set up holds the card back: I run 2 m2 ssds and 8 hard drives in the same case (a Fractal Design R6). While it's a good case and I'm fully kitted out with decent fans (noctuas and gentle typhoons), there's a lot of heat generated from the drives, and my preference is to optimise fans for silence rather than performance. I imagine that in a case with poor air-flow, the gpu temperatures would be equally bad.
For reference, with all the hard drives unplugged and fans running at full blast, my temperatures are under 70 degrees for 850mv/1875 running stress tests (usually 80+ with some clock throttling), which isn't great compared to some of the temperatures reported for other models. Except this was after repasting with arctic mx4, so I'm kinda wondering if the cooling for the Ventus is just not that great compared to say, an Asus TUF 3080. Either way, I'm not too bothered; I don't chase benchmarks, and the difference in actual fps between 1.9ghz and 1.8ghz is so negligible that I prefer to just keep my card cooler and quiet.