Large wire concaves, rotor at 700-800, just depends on how it thrashes. concave at 20, sieves close to the same as wheat. That will get you started. If the milo is dry they will really tear it off in an hurry. Bin extensions, I don't know, only ever used the standards.
Farmerjones, is right. Works great and easy to take down for storage. They make a 8 inch one that fits on the standard deere extension that gives you +- 60 bushels and a 14 inch one that gives you +- 120 bushels. http://www.maurermfg.com/extensions/m120tipupkit.html