Exposure issues

Situation is we have a custom sky as a full screen pass. But I'd like to use the official custom sky hooks. Except our sky doesn't use Unity's exposure.

It also outputs in gamma, which I correct with SRGBToLinear. And it all works fine in our custom pass. The colors match up with the reference implementation. But our sky uses it's own exposure.

So in the sky system where I have to output both pre exposed and not, I'm at a loss as to how to map our sky to what Unity wants there. I'm not talking about just the exposure intensity and multiplier, our sky isn't even using the same range/curve somehow. So part of it is always over/under exposed when using the custom sky api.