One problem with fence height is that if you make it high enough that he can just get his head over, he will spend all his time looking over that fence and after several months will over develop his underneath neck muscle giving him an appearance of a ewe neck.   If it were me I would first try a single hot wire about 18 to 20 inches from the fence in the pen at chest height.  He already shows no respect for a fence and this might correct that in a hurry.