Yes, I always believe it is best to get a ps. Better safe than sorry.
I just made one this morning. I asked for 7:00 am as I believed that is what time they open, I was offered 7:30 and I took it. I was making a ps for 12 people. Don't know if this made the difference or if they don't start until 7:30. I would recommend calling at 6:57am exactly 90 days before date you are booking.