If you have issues with power on power off too much, try using longer lines - this will give you a smooth start !
I dont use shorter lines on my 5 and 3.5 m2 kites, because it will simply kill the dynamics, and the kite will be too much on/off all the time, and no fluid smooth carving left...
Others use shorter lines on smaller kites, I know, so individual - but it seems you have the exact same issues with medium (7 m2) and small kites, so just use std 26-27 m lines and you will be just fine now with a smooth start Neil
The tricky part of smaller kites, if not used to these, is the depower stroke is ridiculously short, so you will either stall the kite, or you will depower too much so it races forward giving a powerspike, and then it is "dead" when at the side of the window
Time and time and time and you will get it - small and big kites DO NOT ride the same at all, and you have to learn this sensitive sheeting - but in time you will appreciate the liveliness and fast turning these kites got, and enjoy the optional powerspike "on demand" when needed.