Chassis flex

I have been having a good look at my new CRT.5 pro kit, and I have opened it up, and started to strip it down (I'm converting it to electric, along with probably a custom Chassis). One thing I noticed, is that the chassis is not that stiff at all. Even just lightly loading it with my hands, there was a fair amount of bending going on. The majority of the deflection occurs in the chassis, between the diff mounts and the chassis braces.

I've just done a bit of searching, and it seems to me that some chassis flex is a good thing. I have a simple question though; why?

I have come from a background of cars like the Revo, and Hpi Baja, where the Chassis are immensly stiff, and are almost impossible to bend even slightly. I also have a fair amount of full size automotive design experience, and the aim there is to have a chassis that is as stiff as possible. My understanding is that if the chassis is immensly stiff, the suspension can do its job better, and it is easier to set up/tune because of this. Basically, the stiffer the chassis, the less it contributes to the suspension pick up points moving, and the easier it is to tune the suspension for different purposes.

On the CRT.5 (and other buggies/truggies) there are braces that mount to the front/rear bulkheads, and the chassis. It seems to me that if these were mounted to the top of the diff mounts (effectively forming a "top deck") the chassis stiffness would increase considerably. I would be very interested to hear peoples thoughts on why there is some flex apparently designed in?

Cheers folks.
Andy