Hello,
here's a picture of my latest Vessel, both as an assembly kit and finished in Orbit. Problem is, on the assembled vessel there is no fuel crossfeed from the outriggers. I can only access the stuff from the core. I built a very similar vessel just the other day (picture) which worked just fine. What's wrong with this one?
To double-check, I assembled the vessel in VAB and rolled it out. Works nicely. As soon as I undock and reconnect a part, however, the fuel in the reattached part becomes inaccessible.
(in case you're wondering why I'm building such a thing... it's a challenge)