Totally depends on how the kite was designed... too short lines on some kites will kill all the power, whilst too long on others will create too much drag and send you downwind. Typically though I would say a 5m would feel best on anything from 19-24m lines. That goes for most kites. My preferred length for all-round riding and freestyle is 24m.
Used 20m lines on my fuel today for the first time. I have always had 24m lines. Found that it was soooo much easier to catch myself after looping. Saving my knees. (I still crash all the time)
I also noted that relaunching was easier too. Great little advantage when said above occurs.
I was speaking to a talented rider the other day. He was using 15m lines and has been getting higher than his kite when looping. He recons it's difficult to get height-need kickers.
I have 25m lines which are fine for my 7,9 and 12m TS kites 
But on my 5m Cabo
Its looks so small and far away 
Unfortunately whenever it gets windy enougth to take the 5m for a spin here on the Sunny Coast
it is usually pretty stormy gusty volitile wind 
So I need to loop it thought the lulls
Which means getting slingshot downwind at a hundred miles an hour,
if you dont time it right between the gusts 
My mates 5m ozone C4 came with 17m lines
But he said it was gutless
I have some 20m lines,might try them next time I take the micro rocket out
What I need is some steady 35 kt wind to go with the 5m kite
