I have been thinking about getting a sling for my HW77 but I didn't really want to drill the stock to fix any swivels in to it. I had a load of paracord lying so I thought I could try and make a sling using the knots I have learned from my bushcraft skills.
The knot on the under lever is actually a not a knot its a Prusik Hitch, it uses friction so it does not slide on the metal. This then has a paracord bracelet clip on it.
I have used 2 Adjustable Loops on the stock, again with another bracelet clip on it.
Then made basically a very large paracord bracelet which clips in to the 2 mounts on the gun.
Nothing new here but I'm quite happy with it.