I just noticed that an update to Project Cybersyn added a new signal called "Fluid Request Threshold", that's not really documented anywhere. How does this work? I presume it sets the minimum threshold for stations requesting fluids, but will the game automatically apply this to JUST fluid request signals? What if I mix a Request Threshold and a Fluid Request Threshold? What happens if Fluid Request Threshold is supplied to a station currently set to "stack thresholds"?

Seems like it's just there in case you want to specify separate thresholds for fluid and item requests (especially useful if you're using stack thresholds for items so you don't get a bunch of tiny fluid deliveries). I did some testing to confirm and it seems to work how you'd expect: the fluid threshold signal (if present) overrides the normal threshold for fluid deliveries only. The stack threshold setting doesn't change anything for fluid deliveries, and you can use both normal and fluid request signals together without issues.

Yeah, I did some testing after posting the question. It seems like fluids entirely disregard the Item Threshold and the "Stack Thresholds" setting on the station. Similarly, item cargo entirely disregards Fluid Thresholds. That's pretty much perfect. Means a station requesting both fluids and items can stay on "Stack Thresholds" and supply both an item stack threshold and a fluid threshold without anything breaking. That's exactly what I was hoping for.