Any ideas on Vapour II tuning.

I shortened the centre line by 15cm by unknoting the line, moving the
sheath up and reknoting it, the kite now turns much faster (pivotal
turning), but apparently flies further back in the wind window ?

I'm hard placed to work out why shortening the line would make this
fly any further back in the window as I would have thought it tended
to depress the leading edge causing it to fly further forward.

Does anyone have any tuning tips, or explanations as to how the tuning
on these kites changes ?

A write up from the loft would be really nice to have.

shortening the 5th line would make it fly forward faster, not sit deeper or shallower in the window. just lets the ktie fly faster through the window.
shortening the 5th makes it more like the flow, pivotal and it doesnt make much power instantly in the turn but gains the power by surging forwards and accelerating out of the turns. slacker makes it have mre power in the turns but alot slower.