My experience is consistent with what Richard said with just Eibach springs. I did not like the way my car behaved on track as it felt "nervous" when experiencing large compressions. Jay at GC attributed this trait to what Richard's chart shows above.
So by eliminating the stock bumpstop with either the Motons or the GC coilover conversion setup - the suspension behavior is more predictable and linear under track conditions. So now I have a nice street ride that I can easily adjust to current road conditions (i.e. press a button) that performs very well/predictably on track.
I'm not a suspension engineer or professional driver but my personal experience supports Richard's thesis/comments....
'15 M3, '15 GT3, '15 Boxster GTS