I found that if you upgrade non combat hulls into combat hulls, it won't un fleet if you exceed your logistics limit. An example of this would be if you had a logistics limit of say 15, and the built three freighters and fleeted them filling the limits ( 15/15 ), and then go to the upgrade screen and upgrade all three ships to the battle ship Exma class ship ( large hull).
Vola! you now have three Exma battle ships in a fleet with a logistics of 18/15 rather then the two ships you would normaly be able to fleet with 15 logistics.

Anyways have fun until this gets fixed!