Nice job throttleboy. I am in the process of getting all my parts together for my build and I chose many of the same parts as you. It's nice to see what my crawler will look like when it is finished.
Just a thought on materials that can be used for limiting flex. How about some carbon fiber strips along the inside or outside channel of the pimp cane chassis? Bolt them in with 3mm screws and nuts.
Or, use some aluminum rods as cross braces in between the channels?
Don't drill or bolt anything on the backbone. It will weakin it. You might beable to Shoe-Goo the CF in place. Test that out first. You can always remove all that easy. I'm working on a material that lays in the channel. Something that is flexible but still sold. Like runner or Silicon strips.