I know what you mean...I tend to way over-analyze these things! (my brother lives in Arizona!)
If you look at the previous bumper stress pics (blue) you can see that adding the added braces in the lower two pictures take the stress off of the welds. Kinda hard to see in those pictures. I copied that off of a commercial product here: https://www.mount-n-lock.com/product...e-safetystruts
So. That helps prevent the 'twisting' on the welds. I understand that the 3 supports I added would apply those stresses if the weight is solely on them. My intent is to have the back part of the tote to rest on the bumper. So the weight would be distributed between the 3 support and the bumper (with the braces keeping the weight off the welds).
Here are a couple stress pictures with 100# on each support and 200# on the bumper. Understand that this is a static load, but it is a good indicator of actual performance.
In the picture with the blue bumper, the weight is applied to the outer edge of the supports. This would not happen as explained, the weight would be even across the braces, but this shows the stress the individual support can handle. The picture shows an exaggerated
theoretical distortion. Where is is RED, it has moved 0.07312" from its original position. The further down the color bar on the left, the less movement.
The yellow picture shows where the stress (green) is on the bumper braces (or struts).
So, this is with 500# total. I won't be anywhere near that, so I think this will work.
The only wild card is the dynamics of driving down the road with weight in there, but I feel confident that it would be fine....