We made roll tarps for ours. got some galvanized tin bent to a 90 degree anle and bent them to fit the top profile of the hopper extension so we have a 3" lip on the inside. We put an aluminum anle iron on unloader side to catch tarp as it rools and a flat iron bar sown into tarp to hold in place on other side with a catch to hold tarp in open position. Run a bar from front to rear extension at the 2 peaks. Put a handle on the front bugee cord holds it in open position, have a gate hinge fasteed to hopper front by cab door to hold it closed. (tension pulls it into the hinge) works fairly well need to go onto cab roof to operate and no spring tension on rear so need to guide by hand while rolling. can be a bit of a pain to fold down but not reel bad , about 10 mins. Not a perfect system but works OK.