Hi Steve. Noticed you didn't get any responses, so thought I'd step in here. Perhaps more detailed questions would queue up some responses. For example (I don't own or have a great deal of knowledge about the SPF product) the spring/shock length should be pretty well known by the manufacturer, but that is only based on desired ride height, and anticipated (desired) suspension movement. For these types of cars, I would suspect a range of max/min shock travel should be around 4-6", with a compressed shock value at static ride height to be somewhere in the 35-45% range of travel from the shortest length. And spring length takes all of this into consideration (as well as spring rate) as well as well as how much preload do you want on an uncompressed shock. It's all generalizations until the details are known.