I am on a DMP too.. Amex is not reporting me late. But they did make strict demands... I am paying AMEX myself because they are not flexible with the due date. My DMP payment would not arrive in time. In order for me to get on the program AMEX demanded four consecutive payments of $324.00.. which was more than double my payment. That was hard because money is tight when you first start a DMP.
There are a few of my cards that will not cooperate with DMP's..
Bill Me Later and Dell.
Chase/Circuit City was a hassle. We proposed a payment of $32.00.. That was denied because the payment was too low. Then we proposed a payment of $55.00 a month. That was denied because the payment was too high. Finally Circuit City agreed with a payment of $35.00.