@paladin2019 - I do take your point. I think for things like ASL, seeing the ground is good enough as we are talking about height differences that are way more than the height of a man. If you want to go down the route of taking into account posture differences in Twilight 2000 LOS calculations then 1 level being equivalent to a low wall makes sense, with some fudging to allow for crouching soldiers on opposite sides of a low wall to see each other's head and arms (weapon levelled). But then you really have to consider multiple LOS. For instance, can you see the target's feet, or their torso?