Once you compress the spring using the device you are describing, you are essentially changing the spring rate characteristics of the spring. You don't want to do that. Get REAL springs... and buy quality springs. Some of the cheaper springs out there sag A LOT after it settles, lowering the car much more beyond what you originally bought in the first place. Also remember to pair up the new springs with a set of aftermarket dampers (or struts, shocks, etc as they are called... but that's a misnomer in every sense) that are valved to handle the new springs. The stock dampers are designed to work with the stock springs... so toss those out.