Cortex gave me excellent feedback.. but in the end it was down to my choices - i just said f everything all that matters is balancing the spring rate frequency front to rear - and 10 sets of coils later i've reached it! what sucks is when i add aero its all gone. i run my S197 soft as hell - 375 lbs/in front and 150lbs / in rear rates. but i've ran up to 600/400 and on a super ultra smooth high speed track it is nice.I can just imagine KW would say that!! Its only the shops like Cortex etc that give you real feedback since they are more focused on one type of car. Would suggest you drive the car and then see what you feel and then start adjusting. Dont go crazy lowering the car too much as that will create all kinds of weird handling. As a first guide, Lower the front until the A-arms are horizontal with the ground but not any more, for the rears dont let the rear control arms down below horizontal to the floor as a max. I like mine with about 2 degrees down towards the axle. Squat and Anti-squat has several useful threads here in TMO.
Coil overs are great but they add a huge amount of variables to the suspension setup!!! The wrong setup will be slower then stock!!!