Chassis flex has been apart of the RC design philosophy for as long as I can remember. Understanding how chassis flex can help is very important, but I have found that each chassis has different characteristics. In the case of a top deck and the chassis keep in mind that both of those items effect the overall ability for the chassis to flex. Flex in the chassis exists in real scale cars as well, but is exaggerated in these scale cars. It is hard to see it but a chassis that does not flex will break!

Chassis flex is used as a tuning tool and makes a very large difference in how the car reacts to many surfaces. Some cars have a very predictable amount of flex and the flex is very linear. Other cars (The ones with multiple top decks) tend to flex in a progressive and less predictable manor.

Most modern RC cars (specifically Touring cars) are design for lower bite surfaces using rubber tires. These chassis need to flex in order to roll and generate the traction required for the tires that exists in the market today.

I recently made a small change to my top deck and this resulted in a huge change in the flex of the car. I felt this change immediately and has been great. But these types of changes don't always work the way you might think. It is best to try different scenarios to find what works best for you on the surface you run on.

Keep in mind that the components attached to the chassis also effect the flex. This would include the bulkeds, motor mount, servo mounts, arm holders, and steering components. When you fiddle with these components they will effect the flex of the car as well.

Like any setup change chassis flex can go too far and start to create inefficiencies within the car. Even though you can make chassis changes in the front middle and rear this will effect the entire car.