Would be interested to hear more about that. A knife goes through anything under tension like butter, but without the tension it's a different story. I would therefore expect the first side (or at least the first of the 4 risers) to go quite easily, but with that release of drag/tension (as the now-only half-attached canopy becomes a very long, thin streamer), I expect the other side would be *much* more difficult. And that's aside from any additional loss of stability being added to the mix.
And as you say, at that point there's still 2 (maybe 3) risers left to saw through.
This shit scares the hell out of me.