I have a customer that continues to have a re-occuring cathedral ceiling crack at the point where the slope meets the flat spot in the center. I am fairly certain that it is caused by humidity levels and some deflection. It is a 2.5 on 12 pitch, and some amount of snow load may be combining to cause extra weight issues. Simply repairing the tape seam is proving to be futile, as it will just keep occuring year after year. I guess my question would be is there a product or solution other than paper tape or fiberglass tape that will bond sufficeintly and at the same time create a more uniform point at which the drywall panels can move without appearing to crack? Something similar to a screed key for a concrete floor which would allow the slab to crack at a controlled point.