ATM, the baseline provided by iracing is very good. I hate fixed series but when iracing provides a good baseline i think they do deserve credit for that.
I'm also attaching a stiff ARB setup. But with the danger of sounding like a douchebag i'm gonna mention it anyway; i takes a lot of time before you're faster with the stiff ARB setup that with the current baseline. I did over 750 races and for this season, i already used that baseline on i think 3 different tracks.
Give the baseline a go before the attached setup. Or if you already use stiff arb, the attached setup may be better.
I heard it time & time again; "Setup is not important in the open mx5". I totally disagree, especially if you have a bit of pace. But are you gonna make a difference by messing around a couple clicks here & there if you only drive the (open) mx5 now and then? No, i think not.
My advice would be to get your mind set to find a setup that you like and stick to it for a couple hundred laps. Even better, drive an entire season with the same setup, will make you much more confident and you'll also learn to catch a slide much faster.
(THIS IS ALL MY OPINION off course....)
EDIT; i added the setups i liked this season. The low camber is for league (endurance) racing. No use for 25min race.