Strange, this example does not compile for me. I had to modify setting of the col widths and some other places.
Anyway, after studying the source code I found that each cell has a field "Borders" which, in turn, contains elements "Left", "Right", "Top" and "Bottom"; and these have an element "Width" for the border width in millimeters. Unfortunately this is initialized with the value 1 mm which seems to be too large, in my eyes - 0.1 mm would be better.
You can do this: Whenever you create a cell call the following procedure: it changes the border widths to 0.1 mm and sets the LineType of the border to tbtSingle (this is necessary because borders with the standard line type, tbtDefault, are not written to the file).
procedure DefaultBorder(var ABorder: TvTableBorder);
begin
ABorder.Width := 0.1;
ABorder.LineType := tbtSingle;
end;
procedure DefaultCell(ACell: TvTableCell);
begin
DefaultBorder(ACell.Borders.Left);
DefaultBorder(ACell.Borders.Right);
DefaultBorder(ACell.Borders.Top);
DefaultBorder(ACell.Borders.Bottom);
end;
...
for iCol := 0 to 4 do
begin
Cell := Row.AddCell;
DefaultCell(Cell); // <---- NEW