The inverted fuel tank is normally placed behind he fuselage frame 5 and is feeded by the aft fuel tank.But, since we wanted to have also a tank for the smoke system we decided to design a new inverted tank that is feeded by the front fuel tank.In this way it is also possible to fly aerobatics with the aft tank empty.
The dimensions are really small, but enougth for our purposes.

 

When you fly inverted in a normal fuel tank the fuel can't flow to the engine since the lines are located in the lowest point of the tank.While inverted it becomes the highest; so what is normally done is to have a flip-flop tube, that works with gravity inside the fuel.

It's important also that the tank has a regular shape, without any interference to the movement of the tube.The tube is done with Stratoflex 156 hose.