Just asking because I depend on the mod to control the rate of adding oil products into a production-line but if I run low on one of the two crackable products I use the less then 80% feature of the mod to keep the cracking to use if it is running low feature (generally I think it is a top-up feature and if I have a separate network cracking everything down then it is reversed with an input and an output [and fyi the input has the less then and the output has the greater then])

P.S. if you wish to keep to your personal coding then if you do so with the mod author's permission have a variable valve (I know I can do something similar with combinations of less then and greater then but this could be a ups saver)

Short answer: I will still look for if any way to do it. But since I prefer to maintain high flow rate as my first priority, perhaps it is not possible under current 0.17 game fluid flow code.

Now the long explanation:
Fluid Control mod (Fluid Must Flow mod as well) is actually using the storage type disguising as pipes or valves.

I have done extensive experiments to test flow rates of different entities and parameters (under game version 0.17.56). An I use corresponding vanilla entities (pipes/pumps/offshore pumps) as control. (I can share the pictures and blueprints, if someone is interested in them.)
In a test of using pipes transporting fluid over 16 tiles, I compared 16 vanilla pipes with 8 storage tank disguised straight pipe (2×2 size each, with 4 times height). I have verified extra fast pump on both ends to ensure the flow is one-way, and full pressure on the first pipe all the time. What I expected is the disguised fast storage tank would have at least 4 times flow rate, and even better than that since only 8 fluid boxes would have less pressure drop.
Surprisingly, the disguised storage tank is much SLOWER than vanilla pipes. Amount of transporting fluid is less than 2% of vanilla pipes. It is caused by more rapid pressure drop, so barely any fluid reaching the output end.
Replacing the type as pipe (so no disguising, other parameters are kept the same) no longer has this unexpected pressure drop. It is 4.76 times in speed, so a bit better than 4 times, just as what I expected and wanted. So it is my current solution.
So my conclusion is there are some unknown bug (in game fluid flow code) causing the unexpected pressure drop, which makes using storage tank as type not a feasible solution, if I want to maintain high flow rate. The valves also use storage tank as type, so probably will also suffer from this.
Therefore, storage tank type is not suitable for high speed flow. Not using code of Fluid Control mod is a consequence, rather than the cause.

When game fluid system is reworked, maybe I will investigate again.

that's okay as I rarely value throughput over a supply/demand balance that I use when dealing with oil