Ok so I rooted, installed the ota, flashed root, and that kernel. I got it booted up and got root checker it says I have root access. But I got a message warning me of a harmful app and need to reboot.
Sent from my SPH-L720 using xda app-developers app
EDIT. i just rebooted and the message is and it is still rooted.
OK apparently that is not just kernel related. I haven't tracked it down yet but I did flash completely stock MDC. I then installed Custom recovery and root. Right after I flashed just the rooted MDL system I started getting that. So it appears to have some kind of root checker in the system.
I am not sure yet though. I have been doing 12 things at once and haven't had any time to dig into it.