CBY, good question - I think you are nearly there though.
In full axle bump & rebound (like hitting a change in height across the full road width) the links all articulate; the top links articulate using only the rotational compliances in their rubber bushes (no radial compliance needed) and the lower links articulate with the standard rubber bush at the front and a spherical joint at the rear. Thus the arc prescribed by the rear pivots of the lower links is different from the arc prescribed by the rear pivots of the upper links. Thus the axle does rotate a little in full axle bump and rebound travel, but this is fine - probably no more than the axle experiences on a leaf spring in use.
In roll (axle articulation), one wheel goes up and the other wheel goes down. To enable this the 2 pairs of trailing links rotate in different directions across the car and 'fight' each other and also fight the Panhard rod. By this I mean that effectively there are triangles formed that resist distortion in roll. Triangles are rigid. So to allow roll the rubber bushes have to deform radially. Thus the stiffness progression in these top link rubber bushes actually sets the roll stiffness. But also as rubber and the bush design are such, this compliance is progressive. So for small angles of roll the roll stiffness is little, but as cornering forces build the forces on the bushes increase and then they really start to resist and progressively limit roll.
For single wheel inputs such as road surface deformations (eg broken tarmac surface) as in roll the rubber bushes in the top links deform and allow small displacement single wheel inputs to achieve good ride without softening the roll in hard cornering. (All helped with the progressive coil spring stack of course).
Thus the front 'RS' and rear '5L' suspensions are matched as a complete car in terms of bounce frequency, spring rate, spring rate progression & roll stiffness progression.
Hope this helps. This is quite a novel approach and is protected by the manufacturer. Regards Peter [PJB]
