We use old conveyer belts out of a local stone quarry on one clamp. They are very efficient and massively unpleasant to handle.
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Drill a couple of holes one end of the conveyor belt and attach a loop of rope. You can then hook them off with a tine on the grab and lay on a pallet when feeding out the silage, and makes them a lot easier to handle when covering the pit. Drilling all the holes would be a good job to keep an apprentice busy!