The other option is to buy camber correction mounts. Usually these are adjustable, and you can adjust it so that you have more negative camber (top of the wheel in) or positive camber (top of the wheel out, and positive camber is bad for performance). They mount on top of the shocks/struts. I dont know the availabilty of these for the G20/Primera, but they are very easy to find for other makes of cars, so I ASSume that there are some for the G20. I think that Stillen might have some for the G20.
Sometimes car companies have fixed camber correction plates. These are also called "crash mounts". Dont know if Nissan makes these. They are used to fix minor camber problems, usually occuring after the car has been wrecked and then fixed, or slightly bent/torqued unibody from pot hole damage and the like.
If your friend wants the maximum performance from his new suspension, then more negative camber is good. Negative camber helps combat tire rolling in severe cornering. When the side of the car is loaded and the car has 0 camber (whel straight up and down at rest), the tire flexes at the side wall, and the contact patch gets smaller, as the tire tries to go one way and the car /wheel the other. This causes the contact patch to get light on the inside, and heavier on the outside, making the overall contact patch smaller. Negative camber helps to reduce this becuase when a car with a good amount of negative camber (maybe -2 degrees or so), as the tire rolls over the contact patch is getting LARGER not smaller, because at rest, the tire's contact patch is favoring the inside of the tire, and under cornering, the contact patch flattens out to be more even across the tread of the tire. The only real drawback to lots of negative camber is that tire wear is accelerated on the iside of the tread.