Overloading the sieves isn't a problem for lexions. If you know how to adjust the combine to the conditions. Thats the reason why you have variable speed for rotors and treshing drum. In hot days it isnt necessary to tresh that agressive...so you have to change the settings. There is no need to change cover plates or anything in my opinion. Instead of rebuilding half of the combine you should have "played" with the settings a bit. It would have been fine than. Moreover a lot cheeper...