RS*R just released their downsprings for the G35 coupe. I found that these are the specs:

Drop:
1" front / 1.2" rear

Spring rate
315 front and rear

the G35 springs are progressive, so the ride will be very smooth.

does anybody have experience with these?

 

Where/what dealer did you find these from? The one Gruppe-S sells drops 0.6" front and rear and are linear springs. The rates for these are 345 front and 417 rear. I'm looking into getting springs too and was about to order the aforementioned ones but I may be interested in these "newer" ones.

Black on Black 5AT Coupe, Navi
350Z Track Wheels by Rays
HKS Legamax Exhaust
350Z Duct
Stillen Hi Flow
7 Wire Hypergrounding Kit

 

those are 350z springs. the G35 coupe springs have the part number 30-N400