Windows custom cursor too small on hi-res screen

Custom cursors (instances of QCursor) make mouse cursors that are too small on a Windows hi-res display. I have attached a simple application that shows the problem. Each time you click in the window, you toggle between one of our custom cursors, and a very similar Qt standard cursor.

On a Dell Inspiron laptop (3840x2160, out of the box scaled at 250%) the custom cursor is tiny compared to the standard cursor. On a Windows machine with standard resolution monitor, the two cursors are of comparable size. On a Macintosh with Retina display, the cursors are of comparable size.