I have always flown mine on 3rd knot from end, working from end furthest from kite. I tried to adjust bridle for rear lines, putting both on front tag, made kite stall when you turned kite. But even if lines are new check them make sure all are same length when bar is pulled to aprox 3/4 of way down.
Tie line ends to post etc, hook into harness, lean back to tighten lines, fully powered pull bar 3/4 way down, all lines should now be same length.
Have had my 13m for 10 months now and have used it in variety of winds down to around 10 knots and have never had any problems. If it pulls to one side all the time check the length of you arms, LOL.



Also 10 knots is pushing any kite of any size to fly properly, take it out in a good 15 knots+ to check it out.