if you can use externals you can send [wm geometry .pdwindow +400+200( to [hcs/sys_gui] (where 400 is x-pixels and 200 is y-pixels)
thanks, yeah ! that's the one i was looking for !
for completeness:
[wm geometry .pdwindow 200x500+400+200( | [hcs/sys_gui]
to change size and position:
[Width_x]x[Height_y]+[Pos_x]+[Pos_y]
best
oliver