Z-linkCobra,
Calm down
There is a vent on the top of the gas tank. I cant speak for yours but the one pictured above has a vent.
I am still waiting to hear from EM as to why the design has a filler mounted midway on the tank.
I am sure there is a reasonable explaination for this because I belive they kept it on the GEN IV model.
Hopefully they will be speaking up soon.