When we first transitioned to 1 sleep I had to keep DS up a bit longer, as he wanted to go to sleep at 9am, but woudl be shattered and miserable by mid afternoon (but refusing to sleep again, of course). I gave him lunch aruond 10:30-11 and he had his nap around 11-11:30. Oh, but then he would have a second lunch too...
It was a struggle for a while, as he would ocasionally fall asleep earlier (like in the stroller or car if we went out), but over time he's been able to stay up longer so will generally go to sleep anywhere from 11 to 1pm (or not at all... but you know...). I try to avoid later arvo sleeps if we can as he then stays up later at night.

From this time he reverted to feeding to sleep for day naps - he was knackered and really needed 2 sleeps, but refused, and so would fall asleep very quickly at the breast.
We also found that around this time, he started to have a longer day sleep (1.5hrs or longer) which was a nice change from 30-40 minutes!