M4 Calibration Question, Horizontal vs Vertical, landscape vs portrait, area?

Is there an advantage to doing calibration in horizontal vs vertical mode, and if vertical, landscape vs portrait?

My Mobile Maslow 4 Frame (utility trailer) will typically be used horizontally, but I could easily lift the front or one side to make it vertical (or mostly vertical, anyway.) I know the calibration was originally designed to be used on a vertical frame, so I’m wondering if that would be an advantage or if it would make it more or less likely that a belt would get damaged during calibration.

What’s a good rule of thumb for picking the calibration grid width and height? Should the grid be as large as possible in the safe working area of the frame, or is it better to make it smaller? Once I get the anchors installed, they will probably be around 2800mm x 1400mm. Based on the frame size checker that @dlang created, my safe working area will be roughly 1800mm x 380mm.

Thanks,
Russ