Ah, thanks for the additional clarification.
I had a naive, early stab at seeing how hard it will be to update flow to 4.16. There were a few differences such as the distance field volume being compressed that I fudged my way around but I reached my rather feeble limit when I managed to crash the shader compiler with some gpu particle code. So I shall just have to be patient and focus on something else until a reasonable time after 4.16 final is actually out (was looking to test whether flow-driven gpu particles work as nicely as I imagine they could with the volume material stuff that can influence the volumetric fog/light stuff that is in 4.16)