JB -
Ron has given you great info on the prices and planting suggestions. I've never planted strips of Sorghum or Milo in between rows. I have planted RR soybeans in WIDE (30 yds) strips between WIDE corn Strips - 50-70yds wide

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It worked really well - especially since I could spray it all at once with Roundup. My beans in the picture are planted about 1/2 the rate Ron suggested because I planted in 30" rows - thus my 50# bag planted about 2 acres - maybe a little more. Next year - I plan to plant 15" rows - and increase the yeild/acre.
Sunflowers are not Round Up tolerant - so you have to be careful where you plant them around RR crops. We planted Sunflowers with corn one year - The did well - but we had alot weeds too. In the end - the deer ignored our sunflowers - but we had tons of birds - songbirds I mean. I enjoyed the plot as much as any I've ever planted - but the deer did not.
We are planting Clover in the fields following RR Beans, This is because we can just "roll" in the seed in the spring (love that round up)- and save on tillage, disking, etc. We are going to experiment with Brassicas next spring too.
We plant RR Beans following RR corn (sometines RR corn following RR corn if the Nitrogen levels are still decent.)
I Don't think you can broadcast brassicas in an established clover plot and expect much. I've planted Dwarf Essex Rape with clover int he spring - it did real well - and was a good nurse crop in a dry summer for the establishing clover.
Good luck - take some pictures and let us know how things work out next Spring.