Wallpaper with Twinview & KDE4

I’m trying to figure out how to get a 2560x1024 wallpaper to fit across two monitors. I’ve tried all the “Positioning” options within Desktop Settings with no joy. I can switch over to Gnome and within the Desktop Configuration settings there is a “fitted” option that works perfectly.

Does anyone know how to get it to work in KDE4.1?

AFAIK that isn’t yet possible with KDE 4.1.x. I think that is something that might be in 4.2, but I don’t know.