Kerry,
Putting a smaller tire on the RR would result in negative stagger(not camber). Stagger from right to left(either front or rear) is the difference in the circumference of the tires as mounted at racing air pressure. Most racers do race with the larger circumference tire mounted on the RR. Stagger affects setups differently on dirt vs. asphalt, with larger differences in stagger usually seen on dirt. Stagger can actually help with turning a car thru the corner, depending on the overall setup(springs, ride heights, weight %, etc.) Camber is the angle or tilting if you will of the front wheels as measured from the spindle. In other words, if the top of the tire is leaning in toward the center of the car, that is negative camber. If the top of the tire is leaning away from the car, that is positve camber. You will also hear the term Caster. Caster is the angle or tilt of the spindle assembly leaning either toward rear of car(positive) or toward front of car(negative). Postive caster results in making front wheels straighten out easier, but makes it harder to turn the steering wheel.
Hope this helps you understand these terms better! Good luck!