Without the use of Dll's why don't you use the X and Y properties of the position of the dialog and -m switch only?
It kinda will be in the perfect position and kinda be docked to mirc window (movable)
I know I cannot do it without DLLs.
What's the problem with dcx ?
It will dock the dialog to the top of the window (channel/query) and the dialog will not be embedded (like its done with WindoFX SetChild), Also DCX will NOT dock the dialog to the left/right of the channel/query window, only to the mirc main window.
