So, I just cut a new set of 10m lines for my NPW and I ended up with one line being almost an inch shorter than the others because of some problems with the sheathing kit. I can just shorten knots on the three other lines and get them balanced, but I'm wondering how significant a difference like this is.

I tried to fly the kite today and didn't have much luck, but I'm pretty sure that had more to do with my wind than the new lines.

It may be easier to just create pigtails or knots in your handle leaders and adjust that way as opposed to redoing the lines,

I like having my lines dead even but lines stretch and bridles stretch and we never really hold are handles or control bar dead even so it is likely something you could compensate for but much easier to just add an adjustment knot on a leader and correct it that way.

I'd like to potentially use these lines as an extension on other kites so just adjusting at the handles won't work unless I always use the same handles when I potentially extend any of my lines.

I figured I'd be able to compensate though since I definitely never hold my handles dead even.

Only one inch differential has typically not been a big enough difference to notice much or any effect in standard length lines...but you are using a shorter line set, so you might.

Try flying first and see.

B-Roc is quite right in the easy fix....

All your handle's lead lines on all your kites should have adjustment knot points( or ability with enough length to tie a knot on any point of that lead line).

Remember...lines stretch...even if they start out all the exact length- this is why you want all flying handles/bars to have these adjustment knots.

Then you don't have to consider using same handles.

Compensating by holding one arm/hand a different length away from your torso does not work well. It can work somewhat..but not well.

Consider:The fact that it is ONLY ONE line shorter and not both brake and power fly lines on the same handle, means simply holding one arm out farther will initially and negatively effect the 'good' line that isn't shorter on the same handle!

So... to compensate for one line longer on the same handle, it would not just be arms at same length so much, as you have to 'rotate' that handle and change tilt( think braking or un-braking rotation) of handle.

I would at least match the shorter line to it's partner. Then everything will at least be equal. You can live with an inch of play between front and back lines without as much issue as just having 1 out.

If you used PKD handles http://www.pkdkitesusa.com/categories/HANDLES/ you would just tweek the clam cleats . I love these. They have a strop between the two,but you can cut and knot it.