Spot basis bids for hard red winter wheat flattened out across the southern US Plains on Thursday after rising earlier in the week, grain dealers said. Farmers booked some sales of the grain when dealers raised their bids earlier this week but most have stopped marketing and were focused on getting their crop harvested, said a dealer in Oklahoma. Some rainy conditions delayed the progress being made in the fields. Protein premiums for railcar wheat to and through Kansas City were unchanged on Thursday.