I use maxtrax with my 10,000 lb van. They flex a lot when spanning a gap, but never buckled. I'm just careful to have enough overlap when spanning a hole so that the flex doesn't allow them to fall through. They can be doubled-tripled-quadruple stacked for more strength and the way they nest won't allow them to slip. They're pricybeing from Australia; there's a company in the USA that makes an identical product now, but I don't recall the name...