I have been using 11-28 here in South Florida, 100% flat except for bridges over highways and the Intercoastal. It may seem wide, but with this cassette I never need the small chainring. Compact up front and 25 tooth in back is plenty for climbing these bridges and the 11 is great for flying down the other side. The big front and 28 rear works but there is some chain rubbing so I really never use it.

I wonder why no one makes a single ring front for riders in flat parts of the country. I think perhaps a 50front and 11/25 or 11/28 or even one of the new 11 speed set ups would be great for many riders and the single front chainring would be lower in cost and cheaper without the physical small ring and associated cables and shifter.