I have a Q2, and there's a large air like bubble on the top of the fuselage, above the header tank. I popped it and gas came out. My question is, if anyone else has had this happened and how they fixed the issue.
This is pretty common for the Q2, and it means that the fuel tank is not properly sealed. The fuel may be eating away at the foam at the top of the header tank so this is potentially a very serious structural issue.
You can do a Q-talk search for "Header Tank Repair" . . . this is what I came up with when I did a search: