saw this problem in another thread and I replied to it and I will just copy and paste my answers in here because I figure it could help all....


I had the super leaker cap on my f4i after denting my tank and saw the front lip sticking up and was going to go with your idea, but I was thinking "WHY IS IT LIPPED UP IN THE FRONT??"

ANSWER; it's because when we smash in the tanks the rear mounting locations distort and GET LOWER than they are supposed to be in relation to the actual top of the hole causing the cap to sit all crooked when it's latched cause the back is actually too low.

SOLUTION just slip a washer UNDER each REAR mount hole under the cap and then tighten as usual and there should be no more gas ***.

NOTE might take some trial and error with washer thickness and numbers to get it to sit nice and flat. I used 1 lock washer on the back of both bolts for mine.