Just thought Id let you know that using this method
http://honai-android.blogspot.co.nz/2014/01/how-to-root-galaxy-s4-lte-i9505-on.html
I was able to successfully root my i9505 without tripping the knox flag :D
I used to be on an old bootloader but i decided to bite the bullet today and update it. I dont think the newer software works as well with older bootloaders especially kitkat