Hi there,
Just wanted to add my two cents too. We transitioned our dd to one nap recently too. One of the things I was advised about was the transition takes time to settle in, in that it can take upto a couple of months for them to finally figure out a time, and take a full two hour nap. My dd took slightly over two months, and only this week has been sleeping for close to two hours, although it was only one hour 15 minutes before. So, if I thought she was getting tired, I would give her a catnap around 4:30 or so, so she can be in bed at 7:30. Now, her schedule is wake up 6:30, nap from 12:15-2:15, and bedtime between 7:15-7:30.
I would just advise you to stick with the transition, even though it might not seem like its getting anywhere on some days. Give your lo a catnap if required, and it'll happen.
Good luck,
Sumita