The kite needs your skilled hand to tune it.
I like mine best with the Z-line shortened with an extra turn around the spreader and the Y-line not too tight, pulling out the x-line only about 2-4 cm from straight. A bit different from what Mr. Horvath says. Also I moved the tow point about 2 cm forward, that makes the kite turn easier.
BTW, nice UN there Erik !!
My tuning was trial and error. There seems to be a fine line between too much Y-line tenson and not enough. A correctly tensioned Y-line allows the kite to go into a nice flat glide.