[itsme]

I crop to the relevant content, usually by calling Auto-Crop first and making small corrections afterwards if required. For one page scores I use Page Scaling Mode "Fit Screen" and Display Mode "Single Page", for scores with several pages I often use Page Scaling Mode "Fit Width" and Display Mode "Vertical Scrolling" (note that both settings have a default setting and a per song setting and are independent for landscape and portrait orientation). I'm fine with just ignoring empty space at the sides or at the bottom.
Nevertheless it would be nice and convenient if I could select a fixed aspect ratio for cropping. It would be especially helpful in case I crop on one device and use it on another device with different aspect ratio.
IrfanView has a nice example of a UI allowing this: