A quick explanation why coilovers tend to be firm. Looking at the above pic, each shock has two springs on it, the thick main spring and the thin helper spring at the top.
In reality, proper coilovers for motorsport use would be specificaly ordered for the application, where the ride height and axle loading and required suspension travel was know. Hence, shocks of the correct length and stroke could be specified. Hence springs of the correct free length (inches) and rating (Pounds per inch) could be ordered, so they fit in the shock and give the correct ride height within the adjustment range of the platform, without becoming loose if the wheel goes to full droop.
However for the general road kits, which have coils over the shock, hence now refered to as coilovers, having a large range of height adjustment for the end user... euro chav look, up to amature gravel stage rally use, the spring rating becomes an issue as the one size fits all spring is needed. Being as this doesnt exist, they use two. The stiff main spring is there to support the weight but must be short enough to get the vehicle low down when the adjustment is near fully down. Also, at this point, it must be stiff enough to prevent the vehicle from bottoming out, hence a need for a relatively high rating, so is supports more pounds when compressed another inch.
A short stiff spring would become loose if the wheel was unloaded, hence the helper spring which has a long free length to take up the slack, but a very low rating so it will be fully compressed before weight is fully on the suspension. So, unless you want to go realy low, you are sacrificing a lot of free spring length for the unused adjustment and the inch taken for the helper, where you could have specified a longer spring, with a lower rating to get a better ride.
All in all, unless your going to go realy low, do it properly and get the likes of ATS to spec the springs for your requirements, or work it out yourself, or dont bother and just fit springs instead and have a lot of cash leftover :roll: