What do we actually know about semi trailing arms?

[Icehouse]

I was arguing with some of the oldschool guys on Facebook, Kelvin pipped up with his car that had the "Penultimate" rear crossmember.  He raised the crossmember to some crazy height in his tube frame car.  Which to me was odd.  I would have put Miata suspension or something good back there before putting the stock stuff back in. Never the less, I couldn't remember how the roll center works with semi trailing arms.  It looks like it's not ride height dependent, it's calculated using the rear swing arm pivots point angles.  Yes a super low car will have really bad squat when accelerating. So for fun I thought I would scan the rear suspension and make a model out of it so see what exactly happens.  

So guys what do we really know?  Looking up pictures of how the roll center works it's hard to see exactly what happens since the sketches are always with level arms......  Is it just squat that makes are cars feel odd in the back when they get super low?  

Yes my model is crude, maybe later I will clean it up.  

[Trophy24]

I like where this is going 

[banzai510(hainz)]

ask a Mercedes or BMW engineer Thats were Nissan stole it from