Solid ladder footing on a slick deck

I recently installed a new deck using PVC decking material. The decking is a great product, but I think it’s a little too slippery to provide a reliable grip for ladder feet. Because I frequently must extend a ladder to reach the roof, I’ve relied on temporary 2x4 ledgers braced by shims driven between deck boards to ensure secure footing for the ladder. This solution works well, but it’s tedious. My alternative solution, as shown in the drawing above, is a movable platform made out of a piece of 1/2-in. CDX plywood, a length of 2x4, and a 1-1/2-in. metal angle iron. The angle iron slips between the deck boards, keeping the platform where I want it, and the ladder feet get a good grip on the rough surface of the CDX plywood. The 2x4 provides extra insurance and anchorage for the screws.