RE: Xfinity 5×1 portrait display + CSV-5400 – will not boot to 5×1 by default

Hi Steve,

You are using an XFX R9 270X ?
What operating system are you using ?

It should be possible to run 4 x 1080p off the MST Hub plus 1 x 1080p off the HDMI output directly off the card.
Make sure the Bios of the mainboard is updated to latest available version ( i know it sounds odd but often really makes a difference) and please make sure Windows is fully updated.
When windows recognized all the screens and resolution and frequency is ok, then go to Catalyst and setup your Eyefinity group. When you are done on the left top in Catalyst yo make a preset, handy to go back to favorite settings with only a few clicks.  

Please also use different power outlet for PC and Screens if at all possible.