M491 chassis is same as 930 sans the tie rods. Im not sure what the ratios are between the narrow bodies vs 930 from the top of my head. The geometry in front is pretty much invisible since most of the parts are the same. Its how the A-arms are mounted to a different front pan that truncates the leverage reaction to the CG. A clue is that the steering rack is closer to the sheet metal pan than the NB were it prevents u from running a large spacer to help with bumpsteer.
For most part I agree with most people here that the stock set up bias towards the safe side for I feel the 930 has even more of an understeer than NB unless u keep your foot in it for some intended hooliganism. This may be due to the anti dive and increase scrub radius over the NB.
How you set up your car is mostly preference and how you intend to use it. If u autox, set the thing up loose unless you like to be spanked repeatedly by a stock miata. Javadog makes a great point. I find entering a corner at over 75-85mph the car turns in much much nicer with heavy areo influence at the rear and less scrub radius effect. Remember turn 8 turn in point at willow springs is 110-115mph. Its REALLY hairy flat tracking around it with your elbows flying around. fun as hell but with successive laps your tires will feel greasy. Its a true widow maker of a corner!
Jack enters at 131mph! he passed by me like I was painted on the tarmac…
Bobby Cee's Racer's Edge: Driving School: The Track
my 2cents pf