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Nd4SpdSe wrote:Actually, all cars are designed to understeer because it's a safer setup

That's what I said. In fact in the link that Marcdh posted, the Mazda engineers who invented the TTL setup said... "a vehicle that is stable under high speed must possess understeer characteristics". It's not just safer, but is intrinsic to a well handling car.

Nd4SpdSe wrote:Inducing understeer would make things worse

I believe that the Twin Trapezoidal setup is designed to induce the aforementioned necessary mild understeer rather than using traditional suspension geometry. I don't know this...but I suspect it. I thing reworking the rear would cause the car to oversteer...which would then have to be compensated for.

Nd4SpdSe wrote:In our cars, we want to eliminate understeer as much as possible.

That's sort of what I meant when I suggested making the car neutral and stiff as a go cart. But you can't eliminate understeer altogether. The weight of the car, especially a FWD car, is biased heavily on the front wheels. With very little weight on the back wheels, a neutral suspension, I think, would tend to oversteer badly. I think that even a balanced race car would be tuned to err on the understeer side. Not to the point of ploughing through a turn, but to transfer the weight of the car to the front wheels when cornering.

Ultimately none of us are experts and so we're all just giving our best guess based on what we've read and been told. I am really interested in learning a lot more about it all. Not just for the MX-3 community, but because honestly, I'm tired of writing manuals and developing training for the oilfield. I want to spend my time doing something I'm really passionate about and this is it.

Ok, like Wytbishop said, none of us are experts, including me. But I do have some experience at the tracks, both on small (R/C) cars and big ones, so I think I can contribute some.

There's a reason why (mildly) understeering street cars are considered safer: because when you lose control you can see where you're going. Other than that, understeering cars are more stable than oversteering ones, because they're less maneuverable (because it's the steering wheels that lose traction first), and maneuverability is antagonistic to stability.
That said, if you have a weight balanced car, with a neutral suspension in all 4 corners, it'll be naturally understeering if it's a FWD, and naturally oversteering if it's a RWD. That is due to the driving wheels having to deal with the force produced by the engine, besides that produced by the car's lateral forces when turning, which causes the drivetrain to lose grip faster than the other one.
The active rear suspension on the MX3 does not increase understeer. On the contrary, what it does is minimize the natural tendency of the car to understeer. The complicated part is to not overdo it, or else you will have an unstable car, that behaves more like a go-kart. That is what makes our beloved MX3 have a much better handling than cars like HHHHHHH..... er...HHONNNNNN.....ugh...well, you know.

Now, to the track.
First, let me make something really clear: there's NO SUCH THING as a "better setup".
What does exists is a better setup for the driver using the car, in the CONDITIONS he's using it.
What that means is that, the same car, with the same driver, in the same track, may need a completely different setup at noon than he needs at 6 A.M, or if the wind pics up dirt and spreads it on the track, etc.
That means, among other things, race cars are setup to understeer or oversteer depending on the circumstances, like the kind of track (oversteering helps turning, so on slow tracks with lots of curves, a mild oversteer is desirable, while in fast tracks with few curves and long straightaways, a mildly understeering car will be more stable), the shape of the track (in a high grip track you need the car to oversteer, or you will miss every curve, while in a low grip or dusty track you'll need it to understeer, or you'll spend the whole race making "donuts"...), the weather, etc.
Also, a car being under or oversteering is only half the picture. Other important parameters are, for example, how abrupt the loss of traction is, or where in the curve the car behaves a certain way. For example, most cars will be oversteering when you enter a curve (while you're braking hard, which displaces the weight of the car to the front wheels), which helps it get IN the curve, they will tend to understeer at the curve exit, when you step on the throttle, which displaces the weight to the back. There's when other suspension and steering parameters, like camber, caster, toe, ackerman angle, etc, come to play.

Hope it helps. Sorry for the long post.