Xtrail the X 3s and even the X2s fly alot more off the front lines than the back lines so it is OK if your back lines are longer than the front

. what i do is hook into the chicken loop (with the kite at 12) and the harness line then set the kite to max power using the center strap (just before the wing tips start to point inwards) but i also ride 80% of the time in both the chicken loop and the harness.
most X3s will fly best on the recomended settings. the only one that i dont fly on the standard settings is my 14 because i find that it likes alittle more back line tension. As it comes out of the bag put your front lines on the bar and then the back lines on the end knot on the leader line on the bar and at the kite end there should be a little red tag on one knot on the pigtails.
let us know how you go.