"How did yoou managed to fit a dropbar in that stem, I have the exact same bike. tried using some screws to open it but even that way it seems impossible."
On my ascent with what appears to be the same stem I used a craftsman flathead and another shim of hardened steel from an old reflector holder to spread the opening. It was about an hour fight to get my Nitto champions through there. I watched rj the bike guys tutorial on drop bar threading through quill stems a bunch to make sure I was rotating correctly. Managed to get it in without scratching the finish. Only problem is now I have to switch out bars again because the nittos are too narrow for my liking.