Thanks guys, I think I can get it from here. Dan, it appears the Whelen is kind of an abbreviated version of your sling but the idea appears to be the same - front and back loop only the front loop is fixed in size with lacing and there is therefore only one (back) claw. I really appreciate you folks helping me out.
If your ever want to talk about J Curtis Griggs mink trapping technique, I am your man.
All the best,
Oldtrapper