Having experienced Stuarts welded diff in all its, errr, "glory"

I have never driven a soft car with a mig spec before, all the ones I have driven have had pretty stiff suspension as well, and with the roll Stu's S13 had, along with a suspension setup from Uncle Bungees house of knackered elastic it makes it nigh on impossible to catch the transition. So I would hold off welding the diff, get stiffer suspension and rollbars, maybe bushes where possible too before getting the diff done. Your car suffers as it is and an S13 is a stiffer car to begin with normally if you follow what I mean.
J.