with ImageCtrl do
begin
  LayersAdd(ielkText);
  with TIETextLayer(CurrentLayer) do
  begin
    Layout := ielBottom;
    Alignment := iejLeft;

    Rotate := 90;
    TextOverflow := ieoShrink;
    Opacity := 1.0;

    WordWrap := False;
    AutoSize := True;
    Text := 'This is my stamp';

    Font.Name := 'Arial';
    Font.Size := 60;
    Font.Color := clBlack;
    Font.Style := [fsBold];

    BorderColor := clBlack;         
    BorderWidth := 6;               // <-- if border ist set, all looks fine

    SizeToText;

    PosX := IELayer_Pos_Left;
    PosY := IELayer_Pos_Bottom;

    LayersMergeAll;
  end;
  Update;
 end;