We had a problem with the 2 gallons of milk staying upright and in the fridge. On bumpy roads the milk would push against the door hard enough to open it or bend the shelf enough to dislodge the shelf. There did not seem to be a convenient alternate place to put the milk other than the top shelf without losing other shelves or bins. I could have strapped the fridge shut, but that would not have fixed the milk still tumbling within the fridge.
My solution was to put a piece of 1.5" angle iron above the shelf and flat 3/4" piece below the shelf and bolt them together. This effectively stiffened the shelf, held it flat even under significant forces and provided a stop so the milk was discouraged from sliding forward. The spacing of the angle iron was designed to be just forward of the shelf and snugly fit a gallon of milk. We still use the spring bars even to help even though they alone did not solve the issue. Pictures are below. We just used it on a 6000+ mile trip on dirt and paved roads and my wife was thrilled with how well it worked.
I hope it is helpful to others. If you have alternate solutions I would be interested as well.
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