The vertical nap has become part of our evening routine. When we're lounging, Wylla will come curl up on top of me, and once she starts getting really drowsy, I'll stand her up with her back feet on my stomach, hold her upright and support her with her arms tucked under her chin. Her body is completely stretched out so any food that's left in her esophagus can slip straight down into her belly. She just stands and purrs and eventually she'll fall asleep. I'll hold her as long as I can, but eventually my arms grow tired, and I have to stop.
She seems to struggle with the last meal of the day more than any other, so nighttime is the best time for a vertical nap.