It is quite normal that at around lvl 75 to possibly lvl 90, you can't see where your shells land. I agree with nyerk
that as long as you can see where the shells land, it should be fine.
When your BO gets to a higher lvl, you will be able to see the line sooner or later, so i don't think it's necessary to BVE your BO too much, although if you are really desperate, or if it's affecting your performance in game too much, it is an option.
However, as your BO reaches an even higher lvl, the line will be way longer than where your shells land, so if you can hang on to it, just wait for your BO to reach a higher lvl.