Omaha, to be honest, I wasn't sure common Bermuda grew that far north. My opinion is just what has worked best for me here in North TX, and I'm certainly no agronomist.
We had incredible rye growth this year because of the mild winter, and we had rye that was easily 3' high.
Mowing it in the spring when the soil warmed up accomplished 2 things for me.
1) It exposed the soil to warm quicker, and helped the Bermuda seeds get to the soil.
2) The rye choppings acted as a mulch to help keep Bermuda seeds in place and retain moisture when they were watered.
When I added my lake, my dam turned out to be 1,050' wide. The rye grass was a life saver for me, and I still fight to keep the Bermuda alive with no watering. It is 104 degrees here as I'm typing this.
If I was you, I'd get with the local Co Op or your Ag store for planting schedules. I'd bet their advice is better than mine.
