Fuel flow issues

[herrozerro]

So I am trying to build some probes with a lot of liquid fuel and I thought I could use the quad adapters. But they don't seem to crossfeed when in the inverted position.

https://imgur.com/gallery/hKZ1P02

Is there any way to do this other than with fuel lines?

[obsidian_x]

I think the issue is the bottom (inverted) one only one tank actually attaches to a node.  The only way I know of is to use docking ports, as they will automatically dock at launch.

[monophonic]

No, they won't feed fuel that way, no matter what. It is specifically prevented to stop some issues with the intended setup. Like, all the engines drinking one of the "legs" in the stack dry before moving on to the next and so on. Causes center of mass to move off center and then the rocket starts to spin uncontrollably.

So fuel lines it is.