There is no any option for tidbits size in the tab appearing, the only two options are those of 'min' and 'max proximity' (body mode, 'monodisperse foam filler' command)... are you sure that you have uploaded the latest version in your downloads page?
Also... when I put the values you said, there appears nothing in the scene...
Also... when I put the values you said, there appears nothing in the scene...