[k@Z@k]

Код:

..... 
private
    procedure WMGetMinMaxInfo(var Msg: TWMGetMinMaxInfo);message WM_GETMINMAXINFO;
.....
procedure TForm3.WMGetMinMaxInfo(var Msg: TWMGetMinMaxInfo);
begin
 inherited;
  with Msg.MinMaxInfo^.ptMinTrackSize do
   begin
    x:= 760; // ptMaxTrackSize.x:= form3.width;
    y:= 570;// ptMaxTrackSize.y:= form3.height;
   end;
end;