Siman

I did 4 inch lift in a 99 Impreza and yeah you wouldn't want to go more than a couple of inches if you wanted it get it certified. Easiest way would be spacers above struts and under subframes no more than about 2 inches. The Foresters and Outbacks have an approx 1 inch shim under the front subframe and probably the same in the rear to accommodate the extra suspension height. You don't get any more travel only ground clearance. You have to be mindful of axle angles, you have to drop the diffs down the same height as you lift the body up. Lots of things need modding that you never think of if you're going large, eg shifter and steering shaft. I had to do radiator hoses and some engine earths too.