However, if I set up YoWindow as a screensaver on my main display, it displays as a tiny box in the upper left-hand corner of the screen - but not only that problem, it displays on both monitors, even though it's only supposed to be on one!
I have contacted the DisplayFusion author, who looked into it, and he states that it's because YoWindow doesn't follow the Microsoft conventions for screensavers and that the fault lies with YoWindow

Any idea how I can solve this problem?
Thanks!