Darlene, I am not "there" yet, but I think I have the answer to your question. I do think the amount of sleep in 2 naps is different than that of one nap. They can get by with less overall sleep when they are on 2 because each nap refreshes them and it's like pressing the reset button. With 1 nap it has to be longer, not only for the total sleep amount, but for the A time before bed too. So I would say a longer single nap should be okay.
HTH
Lyndsy