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Try adding the hoseclamps in the middle. I had a pile of large ones on hand, but two radiator sized hooked together should be long enough to get around it. It seems to give it some structural rigidity to keep from collapsing. Ideally they should be on the inside, but that's not very practical. Gluing some metal rings or sleeves inside would work, though. Finding the right size/shape would be the problem. I only bothered to put one clamp on, but multiple clamps would work better. I was in a hurry.