I shortened the extension collar on my granite gear ozone pack. It was super annoyingly long for me. If the closure system is the same on the Vapor Trail, and it looks like it is, then it should be similar. All I did was cut off about five inches of the collar, sew a channel in the new top of the collar, and put back in the draw cord. Easy peasy. Modifying it to be a roll top as on a dry bag should be a really easy mod, and would allow you to lose the buckles that go vertically and laterally across the top.