[August]

The biggest problem for any modern commerce raider would I'd think be preventing it's prey from getting off a distress call. Gone are the days of having to warn up the ships only wireless transmitter and tap out a lengthy morse code message before having the antenna shot off by gunfire. Nowadays a simple handheld device can transmit actual live video of the attack to anywhere in the world instantly.

Then there is modern military response times to consider. Air assets can be on site nearly anywhere in the world within hours. Like Platapus said they'd get away with the first attack but would not survive for long after that.