I wanted to shorten my lines, cutting and retying them is no problem, it's just the front lines may have stretched and I dont know the correct bar setup to measure them from.

Is it fullpower or depower or some where in between on the bar? and trim in or trim out ?

Well all depends on how you ride, kites generally fly best with all lines even. but do you ride with the bar sheeted all the way in or all the way out??
Out of the box lines are usually set so that when you sheet in the bar with the trim strap at half way the lines are even..
With the pigtails on the lines you can set it up for your own personal prefences on bar power position..
older kites eqlier then 2004 can be run with the front lines up to 5 to 6 cms longer than kites 2005 or newer..
Hope this helps, Have play around and find your own personal prefernce..