Currently, the Grades / Comments / Files window is always present in SpeedGrader on the iPad version of Canvas Teacher in landscape mode. This part of the UI is only used once every few minutes after grading one submission for one input, but constantly takes up more than a third of the width, making the preview window about half as wide as it can be. Some students write small, and the width of the preview window, being narrower than letter size, actually shrinks their handwriting. This makes panning and moving a necessity at times, and squinting a normality to avoid such loss of efficiency. 

Thank you for creating a reliable and evolving platform for teaching.