advstringgrid mergecells and vertical algnment of a checkbox

VCL TMS VCL UI Pack
1

Hi
i merged 2 cells in vertical direction. on this merge cells i added a checkbox. now i want to set the vertical direction to vtacenter. but the checkbox keeps in the top position. horizontal is no problem. what can i do to middle the checkbox

2

This shows a vertically centered checkbox in a vertical merged cell.

procedure TForm1.FormCreate(Sender: TObject);
begin
  AdvStringGrid1.VAlignment := vtaCenter;
  AdvStringGrid1.MergeCells(1,1,1,2);
  AdvStringGrid1.AddCheckBox(1,1,false,false);
end;