Keep the higher junior bars. The mini rise bars will put too much of his weight over the front end, especially if the frame is long. I have a Crupi 0 degree offset stem on JDs bike but I have been thinking of moving him to a conventional stem as he has been growing and is jumping pretty hard now. You can try it out and see if it helps his stance on the bike. JD is running the junior bars btw with the no cross bar.