Then there is the issue with "Return to Sector space". If you think, you end up outside the Fleet Holding's system space, then you are wrong again. You will always end at the point where you entered the first Fleet Holding system space or the point in space where you initiated the Transwarp to a fleet holding. Most annoying and unfortunately Cryptic is not fixing it. They obviously could, as shown with the example of the newest Fleet Holding K-13. If you happen to be there and you hit "Return to Sector Space", then you will end up outside 20 Draconis, no matter where you started from.
Anyway, I made a small chart to help you out. Enjoy.
EDIT: Please keep in mind, that this map only applies, IF your fleet has unlocked the "Transwarp/Shuttle to Starbase" at your Embassy, Dilithium Mine, Spire, Research Lab and K-13.