I used to have a small USB light and also a pen drive both connected at same time to my Tyros 4 an Tyros 5.
However, there were not on a hub, they were each on their individual T5 USB
Never had a problem.
I used the light to better see the music sheets, however, i moved to iPad now, so I no longer need the USB ligth. But used it for a couple of years with no problem.
thanks