Try using a 2nd pair of hands. After your crimpe your material and spin it 3/4 of the way up your tool, have someone hold a skinny board behind the part where your spinning. This will give your material backing as if it were on the tool. Resulting it no buckles. You can also try adding stiffners while you spin. As your spinning up the tool, take a backstroke to the tool. Keep repeating to make steps in your material. Slower speeds are usually better for softer materials, be smooth, and don't be afraid to move the metal... ;)
