Technical seicento - fuel leak while cornering

[meshgrid]

hi,
i have a seicento track car, and an issue with the fuel tank that i've unsuccessfully tried to fix for a while now.
the problem is, anytime there's more than ~5L of fuel in the tank, after a drive on a track (with some hard cornering) i can see petrol coming out of the tank (actually dripping underneath the car).
i checked that the two valves and their gaskets are seated correctly, i think that the fuel pump gasket is also OK, and i don't see it coming from the filler neck. i replaced the fuel tank when this first happened, but so far no improvement.
my main suspicion is the vent hose that goes back to the filler neck - there is no seal there, and all other parts of the tank don't seem to have fuel leak traces on them. it's marked with an arrow on the picture below.
has anyone run into this sort of issue? i'm thinking of either trying to find something that could serve as a seal there (right now it's just the hose and a hose clamp on it), or maybe using gasket maker to seal it (not sure how it would hold up against petrol tho). (EDIT: i think there's definitely something missing on the end of this hose, judging by the photos online.)
thanks!

 

[dac69er]

I had an issue with the tank vacuum non return valve not sealing and leaking. It was with the fuel filler stuff behind the arch liner.

My vent hose is just held on to the tank with a jubilee clip and it is fine.

Do you still have the carbon canister setup installed or just an open vent? Do you have the pressure relief valve still installed on the top of the tank?

 

[meshgrid]

everything should still be stock, including the canister behind the arch liner. i did not check whether any of the tubes were blocked, but if you believe that this could lead to petrol actually dripping out, i'll have a look at that too. (however i would expect that this would happen all the time, also when the car is parked)
i had a closer look at the pictures online and could see that the thing inside the vent tube (marked red on the pic below) was missing on my car. not sure whether i forgot to transfer it from the old tank, or someone already lost it earlier. anyway this weekend i made a similar gasket; we'll see if this fixes the issue.
thanks!