What should the tile overhang be for a verge with a gable ladder?

BS 5534: 2003, Code of practice for slating and tiling states that a verge overhang can be between 38 and 50 mm. However on a verge formed with a gable ladder, 35 mm wide rafters, 19 mm bargeboard and 38 mm overhang, the distance from the verge edge to the ends of the tiling battens is 75 mm. The finished mortar bedding width at a verge should be 75 mm meaning the ends of the battens would touch the mortar, which is not good practice. If the overhang is increased to 50 mm, the distance from the verge edge to the ends of the battens becomes 87 mm giving a gap of 12 mm between the mortar and ends of the battens. It is for this reason that the overhang should always be 50 mm on gable ladder verges. On a brick gable, the ends of the battens rest halfway across a 102 mm wide brick. With a mortar width of 75 mm there is no risk of the mortar touching the ends of the battens with either a 38 or 50 mm overhang as there will always be a gap of at least 14 mm.  more