Talk to Ken at Accurate Suspension 3808 2878, he has heaps of Datto experience and races one. There is a BMW 2002 that he has worked on, similar semi trailing arm suspension, which hauls axe at Lakeside, search Mr Dickie for a recent vid on YouTube, seems to handle great. As a bigger buck alternative there is always MCA of course for the best suspension, I'm sure that Murray Coote has Datto experience. With the right work the STA suspension is pretty damm good eg E30 BMW..
Good luck, keep us informed
Found the Mr Dickie vid
The thing is, the BMW suspension is no better than the Datto's, the difference is that BMW owners will spend money to get it right.