This may have been addressed somewhere, but I’ve been looking for hours... I have a Mac Pro 2010 5,1 with a AMD Radeon HD 7970. I have 3 x 27” Apple LED Cinema Displays with Mini Displayport. I have two connected right now to the the two mini displayports on the graphics card. I understand that Mini Displayport can connect to a MST hub? I cannot find a Mini Displayport to Dual Minidisplayport so I can connect the third monitor. How do I accomplish this?