Thanks, this works (more or less). It leads to a bug: if this is enabled and the window is adjusted to the image, the size of the browser window gets affected, too.
By doubleclicking on the image the window keeps the size of the image and doesn't revert back to the size which the browser used at the last time
BTW: it would be really great if one could hide the menu bar
in viewer only.
BTW2: maybe there's a chance to speed up the scrolling through image albums (clicking next image => next image ...). IMHO XnView should stop rendering the current image when the user clicks "next image" (or scrolls to the next one) and should start rendering the new image.