I lost the old wallpaper Wallpaper Welder made for me and can't now make it repeat the trick.
It looks fine (demoing with a couple of VladStudio images):
but the wallpaper it actually makes looks like this:
so when the image is tiled the left hand monitor is as it should be but the right has a truncated image and a lot of background!
I don't change wallpaper often on this machine and the last time I used it was probably a couple of years back, and Windows has been reinstalled at least once if not twice since then (Win 7 x64, before you ask, and the representation of monitor arrangement shown in the capture of the Wallpaper Welder window is accurate.)
Have I messed up the settings somehow?