Maybe you are just using too small of a kite.
It is true that one and no strut kites work best at the lower end of their wind range, but maybe you are just expecting too much with too little.
I just now realized that most others have suggested the opposite.
I have seen a wide variety of kite-foilers having fun on a wide variety of equipment.
The most important thing is to feel comfortable with the kite you are using.
I prefer to use the smallest kite that will let me top out the speed on my (relatively very slow) 633 surf foil.
I know other riders who get all their thrills from going slow enough to hold down a big kite, and one of my friends is totally stoked about riding his 12 or 15 meter lei (on a faster wing) when I think I am well powered on my 4 or 5 meter Peak 4.
In the end, it all comes down to seeking out conditions where you feel comfortable, and maybe later on, think about what might be possible