Generally the bottom line is for rubber tires, because they are bigger.. the upper line is for foam tires.. foams ar run smaller, and i belive body height is a little lower as well.. I would start with the lower line, measure your roof hieght, then lower it until you got to the legal height desired..
If your club dousent tech body height slam it as low as you can withut the tires rubbing the fenders..
HERE IS MY TRADER FEEDBACK ON HOBBYTALK. http://www.hobbytalk.com/bbs1/itrader.php?u=8257