How to straighten the stabilizer and elevator if they are both downward curved?
Two suggestions: 1. Put some books or boards on the stabilizer and elevator to straighten them if they are just slightly downward curved. 2. Use the hair dryer to blow the stabilizer and elevator. When you do this, be sure to keep the hair dryer with some distance, and be sure to keep the hair dryer moving when blowing. Use your hand to touch the stabilizer and elevator. If you feel a little bit hot, you have to stop blowing and put on some books or boards to straighten them.