Just released: Cube U20GT official firmware version 1.04    U20GT_V1.04_20121122.zip (2012/11/23) 

Android 4.04 build: rk30sdk/rk30sdk/rk30sdk:4.0.4/IMM76D/eng.root.20120824.104436:eng/opinions-on-teclast-p90hdst-keys

Linux Kernel: Linux version 3.0.8+ (root@forise2_linux) (gcc version 4.4.0 (GCC) ) #357 SMP PREEMPT Thu Nov 22 11:58:44 CST 2012

This update seems to be mainly kernel related, Google Translation of Cube version history says this firmware changed the following:

Address aging crashes

Here is our custom rooted firmware version of the Android 4.0.4 ICS based on official Cube version 1.09

Features:

- root with SuperSU version 0.96 (free version)

- writable /system partition

- removed most Chinese and unnecessary applications

- increased space for application (/data partition) to 2 Gb.

Rooted custom firmware for the CUBE U20GT: kasty-cube_u20gt-404-104-rooted.zip

Using Rockchip Batch Tool version 1.5 to flash the firmware.

Please report any problem with this firmware, I can't verify if this custom firmware works properly as I don't own a Cube U20GT  to test it.