NB8A Ride height

[Snowmotion]

When I purchased my NB8A it cam with standard suspension (15 years old) and was sitting at a reasonable height but the ride was not good.

Wheel Center to guard:
Front: 340mm
Rear: 360mm

I purchased a 2nd hand set of Bilsteins from an SE and the ride is much improved and firm but it has lifted the car 5mm. (not much but going the wrong way)

Wheel Center to guard:
Front: 345mm
Rear: 365mm

I would like to change the springs to lower it but not sure about what height I should go to.
I measured this morning and thought it should be around,

Front: 310mm
Rear: 325mm

Can anyone give me advise on a good ride height for a car that is used as a weekend car and will do the occasional track day?
The wheels are stock 15x6 with 195/50/15.

[Magpie]

Your heights will change as your tyres heat up/cool down. Also more accurate measurements can be made at the pinch welds. Set your tyre pressures at what you have them hot, put the weight in the car that you normally have and then measure the height at the pinch welds. 100mm at the pinch welds is not a bad way to start assuming that there is no rake in the car.

[Black_Penguin]

I have Koni Yellow shocks and Eibach Pro-Kit springs and my car sits at 310mm Front and 330mm Rear.
The Eibach springs are around 30% stiffer than stock so aren't over harsh for a daily driver.