I use flow control pipes (and Bob's flow control pipes) a lot, it would be cool if they could be placed underground too

No actual fluid flows through the pipes underground. The underground pipes only exist to control which connectors are part of the same network. Actual fluid is teleported between connectors directly. If you want actual fluid flow controlled, you have to do it on the surface.

ok, Ill do that

I think the main benefit of the flow control mod is the ability to run 2 or more pipe networks side by side without mixing networks

I think the main benefit of the flow control mod is the ability to run 2 or more pipe networks side by side without mixing networks

exactly this, with the limitations of different fluid pipes being close to each other, flow control makes it nice to be able to specify whether or not a pipe piece can ever connect to something else

Agree, what we need is to be able to line up the pipes, it has nothing to do with the others, if possible, we hope to keep iron resources in the inventory