What is the average measurements from arm pit to waist for a young man who is 4ft. 11 inches?

I am making a vest for a young man who is going thru some very difficult times. He stands 4 ft 11 inches and weighs between 90-95 lbs and is 9 years old? It can be flexible in measurements. I need the average measurements from arm pitto waist and waist around? any help given is appreciated. This is a surprise to be sent across country so I can not get the measurements myself and since the mother's English is nil I need some advice.thanks ahead fo time