It depends on how much he basks. Typically it's recommended to have UVB run the length of the enclosure so that it've easily available. You can also have shaded areas, etc. in case your beardie doesn't want that light. I would consider mounting the UVB along the back half way up or something to fan the UVB rays over an larger area...but again it depends on your particular layout and dragon. I know that didn't seem helpful, but you know your dragon and what he likes and where he goes.