I never claimed that we would always be good here, or that we would be good the vast majority of the time. Part of my argument stems that he starts out with the fact that his preflop range is EXTREMELY wide and the range that we are beat here on the flop is EXTREMELY narrow. Obviously he isn't shoving any two, but consider the villain in question here...
OK agreed, but I contend that his shoving range - though he may be a donk - is extrememly narrow also. I suppose this is dependent on previous encounters/hands with the villain and his preponderance to pushing in small pots.

If I'd seen him push pots like these in this session or previous sessions and seen him show marginal hands then I may be more tempted to call.

EDIT: As for my math, yes your right now I think about it... Its not 340/17... His stack is already in the pot so its roughly 350 and the call is 330ish - so 1/2-20/330, so we need the right call (roughly) 45/100 times for it to be +VE.
This correct?