I seem to be getting nonsensical answers for Whistle Stop Factories and Pre 0.17.60 Oil. The problem can be seen with a rocket fuel factory.

I measure it, then build another beacon that will affect it, and then measure it again, the value doesn't change.

I haven't tried that mod, I'll take a look.

I edited in links to the two mods I think are relevant. I haven't carefully stripped down to just those mods to re-create the problem. I think the second mod is less likely a problem than the first, mostly because Max Rate Calculator gets the inputs right, and post 0.17.60 the inputs for rocket fuel changed.

I think it has to do with the factories being so large. It seems like beacons in the middle of a side aren't getting counted.

The game seems to know the percentage speedup and resulting crafting rate for a factory. I've done some modding, but haven't explored this part of the API... Is there a way to query for this information? Of course, that might not work when the beacons don't have power, which is one interesting and useful feature of your mod. Though, one I'd be willing to forgo for the giant factories.