how reliable really partial haging is?

[amaterasu :-)]

Not having in account how easy it is to fail due to SI, I already know that fact. Imagining that the SI is dominated and out of play, and being well planned with a good rope and anchor point, how reliable is this method?

 

[UKscotty]

I would say extremely lethal. The brain will pass out within seconds. Failing the rope or anchor point breaking, almost impossible to go wrong or fail.