I actually have 4.4.4 rooted right now on my device but safestrap doesn't work properly now. It starts to load but then reboots into OS.
The first 4.4.4 rom I made would boot, but only had a black screen (kernel modules didn't match boot.img), then I tried the nj6 boot.img and got the warning about unauthorized kernel. So, I decided to try one more thing. I reflashed the pre-rooted 4.4.4 rom I made and then flashed all of the 4.4.4 firmware in Odin EXCEPT for the system partition. This allowed me to boot into my rooted nj6 4.4.4 rom.