I have no experience with the iron shirt training. But I've seen some wonderful MA's demonstrations where people have taken huge blows and shrugged them off.
From what I've read, admittedly not alot, alot of these demo's rely on the recipient of the strike being prepared to take the strike. In reality an opponent wouldn't be given the opportunity to prepare for the strike. So I'm still skeptical as to whether you could condition your body to take PP shots, without prior knowledge to the strike. I'm sure Mr Rowe will enlightend us either way, if he gets the chance.