Sorry, I assumed he had CAH.  It does sound as if testosterone injections may be the way forward then as otherwise this lad will fall further and further behind his peers.  The booklet I was given by the hospital on Constitutional Delay in Puberty stated good reasons, both physical and emotional as to why you should not delay for too long.  The testosterone will advance bone-age as well as puberty and will not increase final height but it should keep him more in line with his friends,  which is an important consideration too.