I think there is a kit from CIH to drop them down (our dealer installed ours on a 1680, but I'm not sure if all the parts were CIHIJ). The oversize spinners are also available, but pretty pricey.
I made my own, pretty simple really. Had to buy new spinners from case, and do some modifications, like adding extra bearing hangers and some rubber pieces. I've done some experimenting on where everything should be, and I think I finally got it right this year. Would be happy to send some pictures if you want.
Check the mod's button on the left side of the screen. look for a message from spreaderman. He has a chaff spreader kit available. His email is krdexter@ourtown.net