Ground lines are a little bit of a red herring. The issue is not lack of a ground line (horses jump fences with no ground line all day long)…but making sure there is not a false ground line (which can be created by a shadow). so this does need to be examined.
But regardless, no solid ground line will save a truly bad ride. If you push a horse (or a horse rushes) on a flat unbalanced stride to a wrong distance…the horse may chip and not be able to gets its knees up. We have all seen horses step on ground lines when a rider got in the way.
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I personally don’t like fences with a lip (of any type and size) and when I see them in schooling or on courses give them a ton of respect. But I don’t know what research has gone into them…so not sure If my dislike is founded or just personal. I know from personal I’ve had horses catch a toe on lips before…and that is not a good feeling.