This is one of my favorite ledge tricks, and usually a for sure letter in SKATE/ATV. What helps me to get into them is to focus on using your front foot to aim for the coping; when I slide my front foot up the griptape while spinning the bs 180 I imagine I'm sliding it parallel to the edge of the ledge. Most of the time it'll go in like a bs 5050. Another way to practice them is to try bs 180ing onto a ledge, overshooting the coping and making sure you land parallel to the ledge, then taking it to the coping when that is feeling good. I'm trying to learn them on flatbars and they're way harder, getting into the diagonal 5050 lock in is tricky when 180ing into it.