1.5" lowering springs really don't effect it too much. i had the h&r 1.5" springs on my zx3, and never had any problems with oddly worn tires or anything. sorry that i don't have any official numbers for you or anything, but um... yeah. 
anybody want some intrax. thats the last thing left from our various test suspensions for the race car. also as far as camber adjustments. currently using the fc control arms up front, adjusters in rear. we run 2 degrees neg front, 1 degree rear. car is currently being torn apart again (different cage for next year). if time allows my shop will be making true caster/camber plates for the top of the strut towers ala ground control. also may come up with a better lower control arm for the front. i've already had one f/c arm snap, although not on track (close thou-we were putting car on trailer to go racing).