Size of Opus 9 window

I have opus set up in the Dual Horizontal display style (so, I have 2 listers in 1 window). How do I get opus to remember how big the window is? When I open opus and change its window size and then close opus, when I, then, re-open it, the window is a different size than when I closed it.

Thanks,
Ben

Depends how you are opening Opus but usually you just need to use Settings -> Set as Default Lister to update the default with the current setup.