Whtrapta, I like a lot of steel back there. Been rear-ended too many times to not appreciate a lot of mass in the rear armor.
A case in point: I bought a 1986 1/2 Nissan D21 Hardbody truck new, and bought it without the extra cost option of a rear bumper. I made my own out of 1/4" wall 4" by 4" box section steel tubing. The tubing was laid into a full-width piece of 1/4" wall angle steel, and the brackets that bolted directly to the frame were 5/16" steel plate. It was all welded togther solid, and the whole assembly weighed 113 pounds. It paid for itself one day when I was rear-ended by a guy in brand new black BMW sedan. He left the front grill, air dam, headlight rings, and other pieces of his front end on the street. The damage to his car was considerable. I just needed another can of black Rustoleum to repair the scratches on my home-made bumper. This experience led me to the following mantra:
"When in doubt, make the other guy's car bend."