I'm running into the same problem with Concur. But, I'm also realizing that once the booking is complete with Concur, everything gets passed over to DL.

Has anyone had success in completing the booking with Concur, then getting the airline to move up your fare class and charge the difference (either changing the original charge before it's processed or just running a separate charge) within the 24-hour rule?

If I can get that to work, the $30 difference it'd cost me to go from Y to a lie-flat J on a transcon redeye in a couple weeks is something I'm more than willing to pay myself...