Successful finally. Feeling like on cloud no 9
Ya I am also on kitkat 4.4.2 update and is further upgrading to 720.8. My method was slightly different.
After putting stock recovery I was not getting stock recovery menu to choose update and install for update zip file. Instead I relocked the bootloader and rebooted to sense 5( I was on CWM nandroid backup that time). Now from sense 5 I opted to install the update. Waited for like 10-15 minutes (no red triangle error this time) and voila am in official KITKAT with SENSE 5.5 AND ALSO UPGRADING TO 720.8 series....