The height once achieved cannot be shortened by any means however, there are some means to arrest it further by employing the following techniques-
1) If the Peautery- gland is functioning at normal rate, this will allow one to register his height further. To give a break in this trend, one has to curtail the time of sleeping from eight to six hours so that there is less secretion of Peautery - gland so the growth - rate remains static.
2) less consumption of Calcium- Calcium helps in registering the height up to the age of 23 and the same is found in Curd, Milk, Almond, Goose - berry etc and curtailing its intake may arrest the growth in terms of height.
3) You may relinquish muscles - stretching exercises such as Volley - ball, Basket - ball, Cycling etc so that your growth is arreste to some extent.
However, I would suggest you to be happy with your present status any cut in the sleeping - pattern may produce a detrimental effect on your health and hence one must resort to healthy exercises and diets in order to remain healthy.