I have Web Booster installed on the same machine as Domino too. I've always assumed that because Web Booster is set to boost 'localhost' I didn't need to bother with SSL on the Domino localhost.
But I still use SSL for client connections to web booster.
I don't know if that assumption is correct though. Is the connection between Web Booster and localhost secure by default? Does it even get to the network or is the connection limited to the machine only?