Here to help if i can!
I have two SPH-L720T in my shop right now. I have been fairly successful over the years unlocking Samsung devices, but this one has me stumped. I certainly will pull anything that anyone needs from these phones. I have already made the two different sized debrick.img (70 & 128) Unfortunately both of these phones were already updated to 4.4.2 when I received them. (L720TVPUBNC6)
Update: Well so far I had no problem backing up one firmware revision to 4.3 MK5, I did lose sound, and did not seem to gain much control over that modem either. I have been able to register on Iowa Wireless, our T Mobile Subsidiary here in Iowa, and in service mode it shows that I am connected to their 1900 MHz PCS, GSM/GPRS/EDGE, 2G. I have been rather lazy in posting so I do not have enough posts yet to link screenshots. I do have though.