Here we go...
My yardstick is "is safe competition for the ball being allowed or denied?"
The only ostensible difference I see between #2 on the right and the others is the head position, not where the weight is being carried.
I can guarantee one of thrtee things next week (I have this week off):
If I ping it: "Ref, it's allowed"
If I don't ping it, and he gets forklifted: "Ref, he's around my shoulders and neck"
If I don't ping it and there's no forklift: "Ref, he's off his feet. And the only way I can move him is by going high"
Damned if I do, damned if I don't. Thanks USA Rugby. Again. (side note: The last week, from a non refereeing rugby perspective, has not been a good one, and I'm venting)