I wish I had pics of this. I do the same thing and its as fast as a dump trailer. I put down a 16' cable on the floor before loading then when loaded I use a shackle and make a slip joint/knot. I then use a second 16' cable to attach this to an anchor at the grinding station and drive out from under the load. Unhook cables, weight out and pay. On a good day I can do this faster than a electric over hydraulic trailer can dump and drop its bed. The cost is 2 cables and 2 shackles. Pricing 6 hours and $40/hour/guy plus a $100 dump fee. Total $580. That is what I would charge. I can say this that I can fill a 16' landscape trailer in 3 hours by myself with brush. That's cutting, dragging from the back to the driveway and then loading/strapping down. I'm not sure why you would need 12 man hours for a single load or will it be several?