I don't know enuff to say FACT at 150fps... But I can tell you I won't goof with one with a device shorter than more than their length. I have MANY times had them strike and rebound faster than you can see.
I also know the first several strikes are merely warning lunges... The ones that count are with mouth wide agape and the 1/3rd is a minimum assumption... I have seen a four footer with only under one foot still on the ground. Needless to say inertia was a force in action. These are a very strong animal and to think a measly stick on the neck is gonna pin one for long is VERY OPTIMISTIC!
They feel as strong as a mad tomcat when trying to pin one to graps his neck to sack him up.
As for concealment... a coiled pygmy rattler is one of the hardest critters to spot!