you should probably save some money and do it properly with a 4 link, 3 link, or some type of multi link system. tryin to lay with bags/blocks/ and leaf springs is not the best option.
do you still have the overload in? if so, thats why they arent de-arched enough. mine doesn't have the overload and its way de-arched. I also am running the 205/55/16 in the back, only till I can get two more 205/40/16 to match the front.
Run the mono leaf spring flipped upside down. You won't run into anything serious as far as the spring snapping. You're just as likely to snap it right side up.