I don't know how, but fat pirates always look like they are cheating due to their resistance.
Today I hitted one with a pistol, a blunderbus, impossible to be a fake hit from the server since he was just in front of me walking in my direction... and also he suffered a cannon hit from one of my friends (his character has been moved, so I repeat, not a fake client hit, it was real) but he didn't die.
Cannon + pistol + blunderbuss, and he still alive.
And this is one case, it always happens, fat guys have some problem with server hits that made them extremly difficult to kill.
