My spare is mounted on my bumper as well. I've also encountered 2 situations that literally bent the mounting bars for the spare leaving it at a 45 degree angle to the ground and the bumper wasn't fazed. But, BUT...for whatever reason the bumper on my trailer is pretty stout and thick walled. When drilling retaining holes for retention screws for the rubber ends it was fairly thick (for an RV bumper) and is mounted very solidly. That is NOT the case across the board. I have tapped on mine many times to get the "feel of the sound" in addition to pushing/pulling etc. I do the same on most units I look at (never even thought of it, or did it, until I joined this forum). I thought all bumpers would be the same; from my unprofessional, backyard mechanic analysis they appear not to be. Some feel like the square tubing could just be pulled off the back, others feel like if you squeezed hard the sides of the tubing would bend. I've seen some with what appeared to be rust around the welds on the bumper.
As strong as mine appears to be (to me) I would never dream of carrying anything more than a spare on it. I initially planned to remove it and place it elsewhere but on our first trip I bent it out the first time and the bumper was unfazed so I've just left it. Those are just my "seat of the pants" observations - that and a couple of bucks will get you a cup of coffee.
