Steve, you could even go softer since your car is 90% street use.
Probably even 6 or 7 Front & 5 or 6 Rear...............wouldn't go any softer just in case you wanted to do track work.
Been speaking alot to SK, his son Matt and Poly Air Springs in NSW lately.......they are all experts when it comes to spring rates and all agree with the above info as long as you stiffen up the sway bars.
Japs, according to Matt, tend to favour the very hard coilover and don't worry about their sway bars.
He says it may have something to do with their very narrow carports, garages & driveways, lol