TPlanner to display items like background with selection and overlapping


I am trying to obtain the same display of a planner item as background while permitting overlapping.

I have discovered through the code that a background item cannot be overlapped. My main issue is that I'd like to use the same ligne grid as the planner provides without an extra border that marks each item borders much thicker. I tried removing the border without much success, I tried to fiddle around and it all came to the same conclusion : it is not possible to remove the border from an item.
I have then tried to use the background tag in order to not have this border but my items need to be overlapped. Is what I am trying to achieve impossible ?

here are some captures to what I'd like the display to be :
Capture d'écran_20230120_114129

here is what I get without background tag :

and here is the overlapping needed :

Is there any solution to this ?

Thank you

This code was used to show the difference between overlapable & non-overlapable background & non-background items

procedure TForm1.Button1Click(Sender: TObject);
  plit1,plit2,plit3: TPlannerItem;
  plit1 := Planner1.CreateItem;
  plit1.ItemBegin := 4;
  plit1.ItemEnd := 8;
  plit1.Text.Text := 'Overlapable background item';
  plit1.Background := true;
  plit1.AllowOverlap := true;

  plit2 := Planner1.CreateItem;
  plit2.ItemBegin := 10;
  plit2.ItemEnd := 14;
  plit2.Text.Text := 'Not overlapable item';

  plit3 := planner1.CreateItem;
  plit3.ItemBegin := 2;
  plit3.ItemEnd := 6;
  plit3.ItemPos := 1;