FIFTH!?! I'm still on my first tank, it's warped/wavy in the the knee cut outs and spread off the mounts (I've shimmed them out tiwce). For now I'm just enjoying the extra fuel capacity and increased airflow to the intake.I just ordered my fifth GT tank, not even 3,000 miles, all w/o a can.
The "plugged venting" theory is not right. The tanks aren't ballooning up so much as just warping/bubbling/changing shape. I think it's the shape of the tank that causes them to "spread" and fall off the mounts.