As I recall, the crossing dayboards were pretty large, but the passing boards were just in the 'why bother' category. For pilots who cover the same territory time after time, they are little more than a gentle hint. I found binoculars to be one of the greatest aids to navigation. I came along a little too late for the big white X's. When did they cease to exist? As a sign painter, I know that a sign that looks really big up close can shrink to nothing out on a highway, or river. If you are unfamiliar with a stretch of river, you would like dayboards the size of a Walmart, and lights the size of an airport beacon. At which point in time you wouldn't need a radar.