I can see that you put a lot of thought into what you have to say about this topic and what I'm about to say is more my problem then it is yours, but the first part of your post is very long and it all seems to run together and I end up loosing my place. ( mostly it's partly due to my learning disorder and long run-on sentence are very difficult for me to read)
so if you would mind editing your post and maybe adding a few paragraph breaks. it would help greatly.
but I can see that you have a lot of experiences with slings and I hope that I can learn some thing from your post.
thanks for you time