I'm a fan of using double headed trains using Noxys multidirectional trains (https://mods.factorio.com/mod/Noxys_Multidirectional_Trains). Would it be possible to somehow add (better) support for it? I keep getting locomotives that are out of fuel. It's probably because it switches around locomotives.

To clarify, I use <CC>, where < and > are locomotives, and C are cargo wagons. When at a station, the locomotives are like that, <CC>. When leaving a station, noxys mod changes the back locomotive direction, by disconnecting it, rotating it and then reconnecting it. I'm thinking that's why your mod doesnt see it needs to reload?

Source: https://github.com/NoxyNixie/Noxys_Multidirectional_Trains/blob/master/control.lua

Also, what about refuel stations? Shouldn't the station name be based on the length instead of the number of locomotives?

The mod has a map setting that controls the fuel value when a train is sent to refuel.
You could try if increasing this value helps.

About the refuel station's name. Best would probably to have something like "Refuel-2-4-2" for <<CCCC>> locomotives (using your scheme). Or have it configurable with somehow. Hmm. I will think about it.

I saw the setting just after I posted this, thanks.
Is it possible to also force the trains to a fuel station if they have less then 3 fuel slots / have an open fuel slot, instead of based on fuel value?

Well, you know, it's software, so many things are possible. The tricky thing is to allow choices while avoiding too many options to set which nobody understands. I will have a good look at the current code if the "need-refuel" algorithm needs improving.