Tom I think this is impossible. Neither of the solutions above work now and I tried all four orientations of the cube on a single thickness green area with no luck. It was fun to play with the level though.
ColonelFazackerley Neither of the solutions above run to a win for me. (the heart block falls off the back of the platform in both cases). I made one where the heart block ends flat on the floor, but it does not trigger a win. I suggest making the green zone taller, like @Tom suggested. I made one: https://box-stacker.artificialworlds.net/d/317-tank-2 No time to post solution now.