One of the many online 3D printer reviewers posted a while ago a video in which he used a heated ultrasonic cleaner to remove uncured resin. In the process, he discovered that the material will soften under hot water and can be manipulated. It may be specific to the resin he used, but the likelihood is high that you can indeed heat the cape and manipulate it to accomplish your objective.

You may have a problem in this attempt in that you'll be heating the entire item and other portions that you don't want to change may distort. With care and a recognition that the cape will heat faster than the rest of the model, you could be successful.