Not sure at all tbh but I've had 3 live-axle Mantas and they felt much more sure footed than this. The s12 should be much more planted with IRS.
Maybe I should do the beam bushes first ?
Edit: Anyway, this is what I've found so far;
7J x 38et. COuld have done with a lower offset I think
Same with the F2 incidentally. Offset is approx 45, or so I've read.