robert
Expedition Leader
This is true, I was able to maintain these with the installation of my aftermarket bumper. I also believe that there are crumple zones built into the frame itself.
There are; for example, on some models you'll see cuts in the frame that are designed to "give" under a certain load. Some of these are also designed to allow/direct the drivetrain to slide (for lack of a better word at the moment) under the passenger compartment.
Another thing you see on some SUVs is styrofoam in the bumpers like you see in cars.