I'm pretty sure Yao was 7'5 w/o shoes, and Yao was closer to the camera in that photo, so give him another 1-2 inches of photo.
don't think it's healthy for him to pack all that weight on his height. all that strain on his knees and feet
You're measuring the top of Yao's hair, which gives him 2-3 more inches. If you shaved Yao's head he'd be 7'6.