Hattend is right, you are fighting a loosing battle Replace the tank. Sullivan makes a series of Flex tanks. They can be put in places a rigid tank will not fit. Just be gentle installing them. That may solve your problem. Also take a look at Kraft/Hayes tanks. They make a pile of wierd sizes. Maybe one of them may do the trick. Just take your old one to a good hobby shop. They should be able to find a replacement for you.

Mark Shuman