I think the controller should be autodetecting full-duplex capability on the hub, though I've not checked this.

Setting it to fd would not impact the transfer times - the reason for the lack of full bandwidth usage is simply that the protocol running over TCP is the same one that runs over USB and serial - ie, it's an error correcting stop & wait (not windowed) protocol. ftp to the unit can get 1MB/sec sustained: we're planning on some protocol improvements which will help enormously with this.

Hugo