wishy said..
Really short lines will make it turn faster but then you have a shorter power stroke and less good wind hitting it at a lower altitude.
Sorry, Wishy that's just not true. A slow turning kite will not turn quicker on short lines, it may seem like it does but that's because its wind window is smaller, so it travels from one side of the window to the other faster because the distance is shorter. The downside of short lines is decreased power stroke and the ability to work the kite.
The design of the kite is what makes it slow, as well as the physical size. You cannot make a prime mover truck turn and handle like a go-kart.
The early Contra kites were very slow, the later models are on par with similar sized kites.
14M and above normally require a longer bar too, make sure you have a bar that's at least 55cm long on your 14M old Contra, even a 60cm could make a difference, but if its a 10yo Contra, then its just plain slow and there is nothing you can do except retire it and get a modern 14M or larger kite for low winds.