** THIS WORKED ON MY DEVICE BUT IT MAY NOT WORK ON YOURS. APPLY AT YOUR OWN RISK **
Rooted SGP311 (on any Android version up to and including 4.4.2) with custom recovery installed.
If you do not meet these conditions, for example, if you are on an unrooted system, here is a guide to get you on a rooted 4.1.2 with recovery:
This works on locked or unlocked bootloaders. This also works on any customization.
The procedure should work with any pre-rooted Android version but I started with 10.1.C.0.370 (4.1.2) which was rooted with DooMLoRD_Easy-Rooting-Toolkit_v17, patched with remountrebootfix, and equipped with XZDualRecovery.
This process can delete the files on your internal SDcard so back them up. Also, you will have to reinstall all your apps, as they get erased too.
You only need the zip and ftf files. The txt file is just the checksum if you want to verify that your download is error-free. I strongly recommend that you do the checksum before flashing.
1- Backup before you start messing with your tablet!
2- Put system.flashable.zip in /sdcard of your tablet.
3- Keep SGP311_10.4.1.B.0.109_R2C_VMo_US_CA_PR_NoSystem.ft f on your PC.
4- Disconnect any USB cable that may be attached to your tablet.
5- Reboot to recovery. Preferably to TWRP, but you can make CWM work too.
6- Do not wipe anything.
7- Once in recovery, flash system.flashable.zip.
8- It is important to NOT REBOOT the tablet after this step.
9- Find and use the Power Off option in the recovery and turn your tablet off. In CWM based PhilZ Touch it is under "Power Options" -> "Power Off". In TWRP it is under "Reboot" -> "Power Off". If you see your tablet rebooting, force it to turn off by pushing the power and volume up keys simultaneously (or however else you can!)
10- Open Flashtool 0.9.15.0 and click on the flash icon. Choose flash mode.
11- Navigate to where you have saved SGP311_10.4.1.B.0.109_R2C_VMo_US_CA_PR_NoSystem.ft f and flash this ftf with your tablet in flash mode. To put your tablet in flash mode, hold the volume down button when it is off and connect with the USB cable to the PC.
12- Reboot and enjoy!
I only put the files together. All the credit should go to XDA's [NUT] and DooMLoRD and many others...