another step done and posted to make it to usefull for whom it may concern
here the slot once removed the lead weight
...it is clear that is has been done with the purpose to customize the racquet. as a friend of mine said maybe both the stick for EU and US version come out from the same production and then customized.
I have filled the slot with silicon to light the head of the racquets
At the end of all the racquets weight 343gr i.e. 15gr less the before (I have replaced the original grip with a babolat one since thicker and heavier, 7gr more)...and the balance should be around 32cm as you can see...