I remembered that the braking point of those thin bridal lines is pretty high so they wont break if i pull hard on a single one. So I took one by one and pulled it with about 20-30 kg of force and.....slowly slowly one by one.... VOILA! It worked.
Pulling one by one from the attachment point on the kite, I managed to stretch them equal to the other side and equal with the short mixer. Kite now flys like a dream. I'm not sure what Flysurfer recommends for such problem but putting some 20-30kg of pull on those lines to stretch them a bit wont hurt them.
Oh yeah, some people might need gloves. I didnt use any so I don't put excessive force on them but they are very thin and left me some scars
