My local Naish rep explained that you should set all lines equal length with the bar a comfortable distance from you (in other words the chicken loop pulled part way). I didn't used to do this, I set all lines equal lenght with the chicken loop resting against the bar ... but then I found myself always riding with the adjustment strap partly pulled in to get the kite to fly right. Now that I do it the recommended way I am left with the full range of adjustment strap when the wind picks up.
Another thing is that most of us shorten the chicken loop length (by retieing the bowline knot at the trim strap end). Otherwise the bar can travel too far away you. This reduces the depower ability of course, but that is what most more experienced riders want to do one handed tricks.
It is all personal preference.