Just wanted to make everyone aware of the dual boot patcher app. The developer started it for the Galaxy S4 but has added support for many other devices. I tested it on my T810 and it works! Using Neked Nook rom as my primary and CM12.1 as secondary. The official thread is here...
http://forum.xda-developers.com/showthread.php?t=2447534
http://forum.xda-developers.com/showthread.php?t=2447534
