The original geometry rear upright, has the ball joints approx 100mm apart, with one upper ball joint mounted directly above the bottom ball joint, the other mounted on the rear of the upright.
This earlier design has quite unpleasant bump-steer characteristics, and also compromised toe stability, due to the small ball joint separation.
The later design, includes an upright, which is more like a V when viewed from the side, and has the ball joints separated by approx 200mm. The later design I understand resolves the bumpsteer, and toe stability issues.
There are, depending on who you speak to, further issues with both of Marlin's designs. I believe Marlin consider the later rear uprights and the corresponding upper wishbone, provides a car that is very well resolved. I haven't driven one, so can't comment. John (limpabit) has a car in this configuration.
The view of some others, is that even with the bumpsteer and toe stability addressed, there remain fundemental geometry issues, that compromise the car's abilities.
From the old threads, you'll no doubt have clocked what my opinion is. In short, from the books I've read (initiated by my unhappiness with my car's handling as sold), I'm of the opinion that Marlin's geometry doesn't follow typical text book rules, and thus has undesireable properties of a high roll centre, along with poor dive / squat properties (there are other issues, but these are the main 3). This is my opinion, and all I have learnt has been from books / conversation. It could be I'm wrong, Marlin are right.
The only person I think to have sat in a heavily modified car (mine), and a car equiped with Marlin's stage 2 suspension, is Limpabit's friend, Ian (another 5exi owner).
As a slight aside, whatever route you choose, get the suspension (I mean arms, uprights, and shocks to provide the correct droop / travel) chosen BEFORE you drop the engine in, and start to play with driveshafts. I've learnt to my cost this evening, that one of my bespoke shafts is too long for the latest round of suspension mods I've made. A costly error!
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