Hi Gullermo
Just when you think you're done...

Esto no son pajas



Seriously, I don't want to annoying you but when I read the parallel mains connected to UAT, wanted to share this with you. See what happened in this video of a friend F16 with serial tanks and no UAT.
http://www.youtube.com/watch?v=4GXZ6_gzv-M
I vote for option 5 because you have a P80 and probably you are ending up using some fuel from the 3th tank.
Good luck
Nuno