It is my understanding doing this would make me loosing full root. It should be better move to stock ICS first.
Am I wrong ?
Other people may disagree here but in my experience, when moving from any GB rom to any ICS rom I have lost full root if flashing from fully rooted GB to ICS. I think this is why the OP was changed to say flash from stock ICS with full root and not GB with full root.
The difference between root and full root can be seen using Root Explorer.
You may have root, but if you can't mount /system as R/W and copy a file to it or delete a file from it, then you don't have full root.
---------- Post added at 01:16 PM ---------- Previous post was at 01:12 PM ----------
that is the most riskiest method ever! have you guys not been reading?? do not do a full wipe from a LPY Kernel!
Agreed. Do the full wipe FIRST while still on GB using GB kernel.
Do this before flashing anything ICS.
Once you've flashed an ICS rom / kernel - DO NOT DO A FULL WIPE IN CWM!
As long as you follow the above - you
should not brick your device.
I always follow this and have never had problems:
Flash Stock pre-rooted GB rom using odin PC.
Reboot into stock recovery and do full wipe - data & cache (this prevents bootloop issues)
Boot into GB
Install GB CF-Root Kernel for your stock GB rom i.e. if your rom is LA6 then use LA6 kernel
Reboot into CWM Recovery
Full Wipe - Data, Cache, Dalvik (this is safe if you followed steps above as you will now be on GB kernel)
Stay in recovery - do not reboot after wipe
Flash ICS rom of your choice
you shouldn't need a full wipe now because you did one safely while on GB kernel and haven't booted since.