I had Eibach pro's fitted under my 172. They gave me no drop in hight at all! The RS or Cup versions are already factory lowered by default. I had Apex fitted under my previous 1.6 (1999) and was pleased with them, so I also went for Apex for my 172 (2002). Apex has a special spring set for the 2.0 RS. To get a little more drop with Eibach, the Sport lines are often used. However you will never reach the same drop as with Apex. For a drop of 1 cm with Eibach springs I would stick to the original ones. To lower the RS Apex is the first choice. They give you a real additional drop of 25mm on top of the factory 20mm drop.