I guess the first thing is what size are you using? Also, what sized bar and what length lines are you using?
The Generator is a kite that does require pretty attentive user input. Kites that sit further back in the window allow the rider to sit back a bit more and let the kite pull you along, however the down side is that they get bogged down when trying to throw the kite around on the wave. The Generator is a fast kite that flies forward in the window. This means that it is great for generating power through turns and works well when throwing it around on the wave, however when slogging it out on the flats you will need to work the kite a bit harder. This will be particularly noticable if you use a pulley bar that has no sheeting capacity and ride as small a kite as possible. Basically, instead of riding a big kite that you sheet in and out to control the power, you are riding a small kite that requires working to control/generate power.
If you are riding fixed, there is not much tuning that can be done except lengthening or shortening the front or rear lines. Personally, I like to set the kite up so that in 12-15 knots I can steer the kite down to the edge of the window then steadily give it a lift back up to the apex. I will usually initially tune the kite so that it backstalls when I to this then gradually shorten the front lines until the back stalling is just eliminated. This is about spot on for me for riding the 7.5 in those kind of wind conditions. With the 7.5 in light wind, I will be sining the kite most of the time. Whilst this might look pretty laborious to bystanders, you will find that it is pretty easy going once you get your timing right. The fixed bar will let you ride one handed and when working the kite anyhow. Still, when riding in 12-15, there is noone who is out powered on a 9m kite with a twin tip. Usually, most others will be riding 12m+ sized kites in these conditions. I guess it does sound like the kite could have a bit more back line tension from that perspective.