I want my bumpers to not move and crumple why?Because the more they can crumple,bend etc. means the main force to the blow can be directed at the body,and sheetmetal ain't gonna slow down 4000#.

For multiple reasons, I also think bumpers should be stout. But, we can save that discussion for another day.

But, what Doug said above is not quite correct. The more stout and more structurally integrity a frame/vehicle has, the more force is transferred to the occupant. If the vehicle does not deform, the passenger is left traveling at the original speed and is often rudely stopped by the seat belt. Not to mention the internal organ bruising caused by them bouncing around in their own confined spaces.

Crumple zones and the ability to deform absorbs the energy of the impact. Crumple zones are there to save the passengers, not the cars. The general thought is the value of the vehicle is less than the value of the humans within. Some may argue, but...

That said, can we really make a difference in the overall engineered design of the vehicle? No. At the far extreme of impacts, whatever we bolt or weld on will fail at that mounting point. And, at that point, we are beyond saving the vehicle anyway and just hope ourselves are OK. I really doubt any aftermarket bumper has made the difference in a head on or other high energy crash.

The up side is that what we add to our vehicles as protection from the rocks often does the simple task of saving the sheetmetal (or plastic, depending on your variety of Isuzu). That, in itself, is enough of a monetary benefit for all of us to agree with.

Parking lot lunatics, low speed impacts and even rough shopping carts are all less of a worry. Although, beware, this only stands true if you are not the one at fault. If you rear end someone, your bumper may cause more damage, but I doubt it would be significantly more than without it. But, at that point, it is between you and your insurance agency.

Good Luck,
Michael