There are hills in illinois, trust me I got stuck driving those tiny gravel hilly roads for quite a few days last fall hauling silage. We were in the Stockton, Kent, Pearl City area. West of freeport a little ways. There are hills there.
36 row is a big planter, but it can cover a lot of ground.
Local farmer by us runs around 8,000 acres. he runs two 12 row kinzes 1 12 row Deere and a 24 row kinze. Has two newish New holland Combines, two 12 row heads and one 6 row. 2 30' platforms. A slew of trucks and trailers and other equipment. And his biggest tractor is a T8050 New holland. Everything is run with T8000 series or TG series tractors, he has a few smaller New hollands as well. He has an old guy who works for him who loves sitting on an open cab tractor. So he has a little TS series open station that he pulls one of the 12 rows with.
We still run a Kinze 3200 12 row Econo-fold. But were looking at going to a 16 row, possibly with interplant, next because we need a newer bigger combine and that means we will need an 8 row head. But i think the planter we will end up getting is a Great Plains 16 row twin line planter so that we can plant twin rows. We like the idea of 15" rows but if we dont end up chopping the field then we cant harvest is with the combine. So Twin rows seem like a better route. Plus bulk fill is always nice.