Don't get me wrong I'm not saying chassis flex doesn't have a role. Personally I haven't played with chassis stiffness much. I have always used suspension settings to adjust handling.

At somepoint I'll have a look at chassis stiffness effects I just can't say when. For now RC3 just deals with shocks, springs, ARB, Roll centre, camber gain and droop. The nice thing about using a setup simulation is you can look at the effect of many different changes very quickly. It has helped me for sure.