I am using the exact same methods for my camber both front and rear.
#1 - I have my upper control arm out just far enough so it slightly touches the inner fender. It scraped for a while but now is silent as it made a little channel for itself. Camber is pretty good in the front with it this way.
#2 - I am using three washers but yeah it is not enough. It is wearing my tires unevenly with the front and rear camber the way they are (rear is little worse than the front), but not too bad. I would like to fix this eventually (at least the rear) but I think we'd need to buy a new upper arm. I wouldn't feel safe going more than 4 washers in the rear.
Oh yeah I also have Neuspeed Sport springs...