what is needed to be done to the rear springs in the 1200 to make them firm enough to drive fast around corners.

i know that you can add another spring, do you just use another set of 1200 springs and take the main one and add it to the rest of the set.

also whats the best way to go when lowering them, to use lowering blocks or to get the eyelets reversed, and what does this normally set you back $$$.

if there are any other options for firming the back end up please let me know.