No idea about dead hangs specifically, but good posture (which requires strengthening the right muscles) probably adds a fair bit of height over bad posture, an

No idea about dead hangs specifically, but good posture (which requires strengthening the right muscles) probably adds a fair bit of height over bad posture, and bone can stretch slightly in response to exercise. That said, the benefits of good health, better confidence, etc. from strength training probably far outweigh any benefits from increased height.