well let me inlighten you. we do this test at work for sensors. we use 80 feet of 1/2 chain. we hook to something solid like a road grader(over 30,000lbs). we then hook it to the back in the vehicles at the Hitch. we have a solid steel hitch block our chain pins into, we then pull it 10 mph till it comes to the end of the chain. its a very solid point as the vehicles stop abruptly. now if you pulled like that on a frame corner you might not be going down the road straight afterwards. now to get to the point of this. I used to do frame work in a body shop. the pulling force to straighten an old CJ frame that had been diamond shaped was around 30,000 pounds of pull. so consider what it took to put the diamond in the frame?