Having run a 12 row heads for eighteen years, I think I can offer some insight. One 750 bushel grain cart works good on one half mile rows, a 1000+ is necessary in 3_4 mile rows. In half mile rows, the combine tank really needs to be large enough to make a full pass. When the combine turns, the cart needs to be there, ready to catch. If the combine can't make a full pass, the grain cart can't unload fast enough to get back under the combine before he fills if the combine is running at or over 4 mph. That said, a twelve row can be incredibly efficient. Several neighbors have recently switched from 8 rows to 12, and are amaxed at the increased capacity. Before, they had to run an 8 row so fast to keep the combine full, they ran over corn, or had to slow down anyway in less than perfectly standing corn. With 12 rows, we move at a steady pace, never outrun the header, and keep the machine full at all times. Good luck
