I was more referring to the concepts of how to determine the amps per port rating, and my suspected yet unconfirmed notion that the power regulation devices within a given hub work usually in pairs, so that you can safely draw 1.8a out of one port in a pair of ports on a USB 3.0 hub.  (and that a 9 port with 3 power switches is probably regulating 2.7a over three ports)