Well tried to crossflash my K770i to W880i.
It didn't work at the first place. Had some issues with the display.
I replaced the display and camera drivers with the original ones from K770i.
At my surprise, it worked! All satisfied I pressed Normal Startup and tried to enter the PIN number. Then... disaster! The keys sequence was all lost. When pressed "5" the output was "1", the power key was the "C" key, and keys were in general all messed up. So you couldn't get the phone turned on beacause you couldn't input PIN number correctly.
This was not expected from me because the keys are all the same in K770i and W880i. So I was frustrated that this one did not let me have a walkman player on my K770i.
Maybe this can be fixed with a keypad patch later.
This was posted on order to inform Top Sony members of this procedure.
No responsibility will be taken for damaging your phone software/hardware/etc.