Are you sure it is Chassis Flex? As I had problems with my motor moveing what it turned out to be is that the long bolts that hold the motor in on the RTR Motor mounts would loosen up just a bit when they got warm. Just enough play in it that the motor would move when you blip the throttle. As soon as I got rid of the Motor mounts and went to a bump box that problem was gone.
ORIGINAL: aangelet
I don't know if this has been mentioned before, but have any of you noticed how much chassis flex there is in the RTR version? Mine has tons. I can actually see my engine moving when I apply the throttle/brakes. I suppose that the Pro version with the 7075 aluminum and the milled cuts are more rigid, but the RTR's chassis is almost like it's made of rubber. I was going to get a pro chassis, but I've been getting the standard chassis for $26 on ebay. I bash a lot and bending the chassis just isn't that unusual for me.
Last week, I picked up a set of engine mounts for the Mayhem ST and adapted them to my buggy. Now most of the flex is gone and the chassis is much more rigid. I could actually feel the difference on the track. You might want to check it out.