I haven't tried this with bigger VMC Siwash hooks, but in 6/0 and under I can compress the barbed section back towards the shank with my fingers. And I'm not the strongest guy in the world--far from it.
Stainless Mustads don't bend---they just break. Very brittle metal. If the shank doesn't go, the eye will.
Tinned Mustad Siwashes used to be good---haven't bought them in a few years. Their trebles have gone down the tubes, tho. Something to do with having to eliminate cadmium in the alloy used, or so I've been told
