We also have an about a 6’ feed line mid course. We secured a couple of feet of chain to it to make sure it sinks when running the course.
To find it we use markers on the shore line. One side a dock and the other a shed and drag a hook with the boat pointed between them perpendicular to the course. It usually puts us within 10’ feed of the feed line then we just pull ourselves over to the feed line. Our lake is also to murky to see the course when down.