I’ve encountered a similar issue; heat guns can bend the plastic too much. Using a hot water bath (nothing boiling) has worked better for me; immerse the belt for a short while until it becomes somewhat pliable, then gently bend it into position. To avoid distortion, it's a good idea to place the belt between two surfaces with comparable shapes while it cools. Reinforcing the area with adhesive (E6000 works well if you rough up the surface beforehand) and a small amount of ABS paste inside can be a lifesaver if there is any cracking or weakness. After it has dried, sand it smooth. Has anyone tried a comparable technique or discovered a superior do-it-yourself trick?