"Dirt" - i.e. top soil, organic layer with a bit of sand etc. - if not obviously wet, you should run out of room before you run out of carrying capacity. With 5 yards loaded, the Deuce looks visibly full, with a mound in the middle and halfway to 2/3 up the sides, and you will be at or around the 11 ton mark on the scales. An empty deuce weighs in at around 6 tons.
Last time I picked up river wash, the loader had a 5 yard bucket and approached my truck with that bucket heaping full. I am sure the loader driver had a laugh. Me, less so. I had to shovel quite a bit of that load off, in order to stay semi-legal. I find that, with 5 tons in the back, the Deuce is a heavy as I would want it to be and still slow it to a standstill.
Please do not forget securing your load if you go onto public roadways. At the minimum you will need to brush off loose material from the sides and tail gate and cover the load with a tarp or a net, securely strapped down. A friend of mine dropped a bit of gravel, courtesy of pot holes, and peppered a cruiser behind him. Did not go down so well.