QA1 Dynamic strut rod. OOPS

No, I do not have plates but it seems that many have used flat plate lubricated in between or trash bags. I was going to try 6 mil poly, 4-6 layers.

That will work, you just need a smooth surface and lubrication so the tires turn smoothly when you turn the wheels. Grease between two aluminum plates works fine. Even just plain dish soap on a polished concrete floor works ok. A poly plastic and a bunch of dish soap should be fine if the concrete is relatively smooth.