I shut down our operation at Atomic sadly....... I re-wrote the geometric settings for the IS200/ 300/ SC some years back after the owners of this forum contacted me regarding the issues members had with front tyre wear, sadly Lexus got it wrong!
As for the modified IS or any car in reality that's a completely different story. Calibrating the chassis leans toward tyre saturation limits and this in turn depends on suspension, bushing compliance with a mix of duty, this being the expected role for the car?
The hardest thing to calibrate in my opinion is you :o ..... Now the car is low with coilovers fitted and the desire is fast, flat high speed cornering..... Well how fast? How flat? How planted do you want the car, do you want to read/ feel the saturation or snap oversteer?
Getting this information is difficult but essential otherwise one owner could say the car is un-drivable and the next driver love it.The reason for this is the human and the car chassis has a frequency, lets say a manufactured easy level that's easy for us mire mortals to drive. Modify the car then everything changes, either the human frequency ( input ) or the cars reaction, both ways there's a telling factor the geometry calibration needs to address if only to dumb the cars frequency down.