If you were able to use a 1mm piece of Aluminium scraping along the floor, then I assume that a 1mm piece of steel should hold up as well?
Hmm... The design of my hinged plate wasn't flat like you are proposing, I had added a bend into it prior to the event but even without it, I still seriously doubt it would have survived, even if it was Steel. I still think that this was because it wasn't supported by anything. Had the wedge followed the contours of the leading edge of the HDPE beneath, it might have stood up better.

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