I fitted some lowering springs to our RCZ some six or seven weeks ago, the main thing that attracted me to the idea was a post on the Facebook RCZ page from another RCZ-er who said that the ride quality was much improved. These lowering springs are often described as being `progressive ‘with wider spaced coils as well as tighter spaces, the idea being that there is greater initial flexibility in them (softer). I went for a brand called Pi as they were the at the budget end, and if they didn`t work it would be no great loss. Definitely soften up the ride, took me around 4 and a half hours to do all four, and the only specialist kit was a spring compressor, had the steering geometry checked afterwards, as the drop will alter it.
An earlier mod was to change the 19" for 18" wheels which was a help, and as an earlier poster said, do check your tyre pressures (when cold)