Correct....

Imagine that you don´t have the 3th tank and have only the 2 mains in parallel connected to the UAT. The mains are very long with a reduced height. If you run those in parallel a make some manouvers or turn too much to one side, you have a serious risk of letting air going to the UAT, specialy after the first minutes where fuel level in mains is low. It happen to me in the first flights and then changed the set up in the mains for series. Also happened twice in other 2 F16 here. All have changed to series.

If those tanks were built in height rather than in lenght, you would not have this risk so high. I strongly recomend you not to use parallel without the 3th tank or a high volume UAT.

Regards

Nuno