I know countless people have had this problem and before i try to put my gas tank on my rear rack back words and have it leak everywhere i figured I'd try to figure out a solution to the problem. I know if you seal it up better between the neck and the cap it'll create a vacuum. If i sealed that up though and drilled holes in the cap for it to vent would that help at all? I wouldn't need to fill it to the top. I've looked for other gas tanks to mount to the back but i can't seem to find anything that'l work great. Ideas..??