Yeah only at the End Points of Item Pipes, you cant put them in the middle of Pipes. The Routing Mechanism is based on scanning the entire area and then always trying the shortest path possible, completely ignoring which pipes have let up to that path for performance reasons.
Oh right that. I cant put actual Fluid Container Values on them, and in hindsight I should have made the Glass Tubes like Measuring Pots instead of Meta Items. The reason for it not containing the Fluid using Fluid Registry is its 1/9th of a Unit, so for a Fluid that has 1000 per Unit it would round down to 111 Liters, but that is less than 111.11111111 meaning it would result in a dupe. If I do 112 Liters its more than 111.11111111 resulting in an even supier dupe.
Though I can add a special case for the Tubes. Sure.
Edit: Added it, wait 10 mins and it should work in the secret version XD