458 458 Novitec Lowering measurement help please

Hi

I wonder if any of you fine people may be able to help me, I've searched the numerous threads with regards to lowering the 458, but not quite found out the info I'm after.
I have Novitec springs that I'm going to be fitting. I'm basically looking to find out the correlation between the number of threads left visible on the shock in relation to the actual height of the car. for example if I move the collars on the shock down 10mm, will that lower the car 10mm,12mm or 20mm etc?

I basically want to try to work out how many threads to leave visible on each shock (with the Novitec springs) and what height that will leave the car at.

My car has the lifter so is likely higher than a non lifer car. so to remove that variable I wonder if anyone has any data that relates to ride height against number of threads visible on shock with Novitec springs (or collar height from bottom of thread)?
To clarify what I'm calling ride height: I'm calling ride height The measurement from the centre of the front wheel directly up to the arch, which on my car is 395mm, or top of wheel to wheel arch (measurement point doesn't really matter as its all relative) To move that figure by 20mm how many mm lower will the collar need to go on the shock? The same question for the back shocks? I assume they may be different due to different shock angles and linkages etc.

I basically wanted to try and work out how high to have the collars on the shocks with the Novitec springs to start with to avoid me having to keep adjusting them on the car, or worst case have to keep taking them off to make adjustments..

I'm not entirely sure what ride height to aim for at the moment but if I can find out this info I think it will possibly avoid me doing unnecessary additional work.

Any thoughts greatly received

Thanks Miles