this is an old thread, but in case somebody else stumbles upon it later... you can use standard xorg geometry parameters, for example :
Code:
kdialog --msgbox "i'm elsewhere" --geometry +900+600
original syntax is
Code:
1000x1000+0+0 or (xsize)x(ysize)+(xoffset)+(yoffset)
but i don't think size works for most kdialog output modes