Here's a thread on it
I found this video the other night of this gentleman using amsteel and a loop alien to attach squirrel steps to the tree. In a comment he left on the video he states that he feels it’s unsafe as the loop alien isn’t weight rated and I totally understand that sentiment. But I don’t know if it...
saddlehunter.com
The loop alien is not rated because it is not advertised to be used for holding a human, it's to cinch up various cords for camp and other uses.
However, the guy that put that video up is in the thread and has good things to say about it. You could buy a cheap crane scale that doubles as a nice bow scale and use it to test the loop aliens with a hand winch. If they will hold 600 lbs in your configuration, you should be good (or whatever pounds you want).