I assume vent for rear tanks is lower than front tanks fuel level and level in fronttanks higher than rear filler when full. So does petcock have to be turned off until front tanks empty a bit?
I guess there are many raer racks out ther ...many different designs so hard to plan best location on rack. On other hand Unless your globe trotting then most likely need for extra fuel is a long days offroading (low mpg) when its unlikely you have luggage on. Then tank filler in rear rackis the 'cleanest solutio, and being higher than underseat might help with issues above?
Underseat is not so bad.... OH OK I don't know the answer!!
Very nice work though
990Adv, little talent