hi all
the 105 front derailleur solved the issue.
definitly less tension on cable is requiered, shifting light a charm.
Conclusion : Sensha front derailleur is crap and may even damage your frame (inserts).
I've been riding "IRL" this morning. 75km and wouaaaa the bike is really nice
still some adjustment and fine tune here and there, but yes the frame react well and it's a pleasure to ride
more pics to come