oh my gosh I’m so flattered!! I don’t use the same size canvas everytime, what I do first is sketch the full body pose I want, then I crop the canvas to fit the sketch itself and use the move tool to center the piece, I go back and forth between sizes, if I want to add more I make the canvis bigger and if I want less I shrink it, I draw on my phone too! so I think you have that feature as well, the canvas size option is on the top left of the “frames” tab. hope this helped!!!
