The typical GT40 chassis is much more complex than the simple rectangular cube. Basically though for max torsional rigidity you want to somehow connect all the way from the front of the front suspension to the rear of the rear suspension with 3 dimensional rigidity.
This is problematic especially given the door opening (across the roof). The original cars solved this problem by carrying the rigidity across the cab of the vehicle through the rocker boxes (side sills) which serve the function of rectangular cubes. It probably happened the other way around though, in that the rocker boxes were designed first for rigidity then the door openings had to be moved up so they would be large enough for access. Either way the kits all copy the original doors so somehow they have to carry the rigidity through the cab in other places. Since the large side tanks have no other place to go this rules out a central tunnel like the Lotus.
So this then becomes the weak point of the design. Either the rocker boxes have to be duplicated through tubing or sheet or it's going to be weak in the central area.
With all this information look now again at the two previously posted chassis pictures. Think of all the "sides of the box" left, right, top, bottom, front and back. How many sides have triangles? The one with more triangles will be more torsionally rigid.
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More on the benefits of torsional rigidity.
Good handling on the turns depends on all four tires keeping in contact with the road. The shock absorbers function is to achieve this as well as possible by absorbing bumps, irregularities, road angle and changes in vehicle angle due to cornering, accel and braking loads.
Coilover shocks consist of a spring to adsorb impact and allow movement and a hydraulic damper to control the springs movement and oscillation.
The racing shock absorber is a very refined mechanism and in order to work properly it must be anchored on the fixed end by a method that holds it stationary in relation to the rest of the chassis and the other shocks. The shock is trying to hold the rubber on the road with an even amount of force in relation to the other 3 corners if what it's anchored to isn't stationary it can't function properly.
Another thing that happens with a flexible frame is oscillation. In essence it becomes an undampened spring. It receives a load and springs in one direction then springs back and forth until the oscillation dies out. If you've ever driven or seen a car going down the road with blown shock absorbers, all the fluid is gone so they have no dampening. The car hits a dip in the road and springs up and down several times before leveling out. Certainly not conducive to good handling.
A race car has 3 basic requirements, horsepower, braking and handling. Or go, stop and turn. You've got your mega$$ dynoed fire breathing powerplant, all you do is floor board that pedal. You stop fine with your mega$$ 14" rotors with 4 piston calipers all the way around. You should have the turn no problem, you've got the mega$$ tires, suspension, shocks, but what about the foundation, a rigid chassis? Have you "dynoed" it's performance? IMHO FWIW, if you don't have 6,000 lbs/deg. plus your taking that turn with a "150 HP" engine.
