Sort of trying to revisit this topic as my JRZ order was finally shipped and my mechanic has told me into going with 600/700 lbs springs with it as he has firm believe 200lbs split from front to rear is too much and causes too much of oversteer what is difficult to tune.

I spent quite some time then looking for an info and got to say opinions differ a lot. Seems like majority of folks prefer 600/800 springs but it is sort of a migrated choice over from 993 cars world, plus that 200lbs split is not nearly 'a given'. TPC`s mr. Levitas suggests 900/900 springs as the best option. Some folks believe either 750/900 or 550/700 is best choice, and most advanced say it all must be track dependent and like for lime rock even 600/800 is too stiff but for watkins glen you need way stiffer springs above 1000lbs area like in cup cars - 1200/1300 or so.

Still most agree that anything at or below 450/600 springs for 997 cars is too soft. without specifying why exactly.

All that is pretty interesting indeed to read but what worries me - apparently all that is mostly smoke and mirrors, there are no mathematical models of any sort or computations to put behind all those 'suggestions' nor to mention tires and sway bars are not usually even taking into account where one would expect it to be incorporated...

I was generally trying to establish some sort of statistics on how do people compute proper springs split ratio but was unable to get it formulated clearly enough, at least from scanning rennlist and this forum.

Not sure what I am trying to say here, mostly probably - I was quite surprised not to find any scientific engineering backing for most of those 'commonly known solutions', or at least that was my overall feeling. As my mechanic prepared dozens of 996/997 gt3 cars i will simply surrender to his suggestion as he does those jrzs all the time but still, it is quite confusing. just my 2c.