Dependent on kite but as a rule:-
For a four line, equal length bar, set full power with lines at equal length about 1" (2.5cm)from the chicken loop this will give a tiny amount of back stall for jumps.
This will help ensure the kite doesn't over fly you (go over your head in a jump).
Any doubts pm griffinkites
www.seabreeze.com.au/Members/Profile/Details.aspx?member=GriffinKites
and I'm sure he'll give you the lowdown

Above sounds about right but i would go for 2 inches from the bar 50mm,when your set and flying the kite try it in about 10-12 knots,pull hard in with the kite at the zenith and see how quickly the kite stalls if stalls straight away go a bit shorter but if it takes a while to stall then sweet,if it dosent stall at all you could go a bit longer.

I usually set all my bars up the same in 10-12 knots no matter what size kite ,usually its easier to stall the kite in this wind so you get a better setup,kites tend to stall easier when loaded at the bottom of the window so if you set it to stall in stronger wind at the zenith then it will fly like crap when loaded up at the bottom of the powerzone, but if you set it to just stall in light wind then its normally way harder to stall out wide open in its windrange.

You can adjust for line stretch if you fit the right set of pigtails.

Not disagreeing with Todd or radman4 here by any means. A bit beyond the bar for centre lines is a good idea once you know what you are doing. BUT - and its a big BUT - for beginners the VID & Griffin advice is best. Tuning to same length on full power at the bar will create less kite control problems for those at the steep end of the learning curve.
When and if you want, and can use, the advantage of some over-sheeting then yep shorten your centre lines for sure.

Small length variations are simplest fixed by allowing for the known irregularity by using the knot options at the kite end pig-tails (I know its cheating and not fool proof but its easy )

radman4 said...
i like to tune the bar to the kite though as you cant always go with the all lines equal length theory

Absolutely. Its definitely a 'theory'. Works in most cases but we had a newbie in one day with a new kite he claimed 'wouldnt fly right'. Tested his lines - spot on same length. Tested the kite and found the only way that particular kite would behave was to lengthen one set of lines by a full 100mm !!!
(wont mention the brand)

radman4 said...
On all my bars i have a leader on the steering lines that is about 200mm long with equal multiple knots,this allows quick adjustment and its great for quick adjustment for different wind strenth,also allows me to use the same bar on many different brands of kite.

Nice work - I like it.