adjusting column widths in user_email_body messages

Hi Tuan,
Is it possible to adjust the width of the columns used to display the fields in [REGISTRATION_DETAIL]?
Ideally, I'd like to have an option to have the field names all remain as single lines, instead of some of them being shown over a couple of lines.
The attachment shows what is currently happening.
 

In the source of the email that is sent, I can see the following for .title_cell.
.title_cell
        {
            font-weight: bold;
        }

I'd like to try to change this to include nowrap:
.title_cell {
  font-weight: bold;
  white-space: nowrap;
}

Is it possible to do this as an override, so that it doesn't get overwritten by updates? If so, where do I do it?
Thanks in advance, Peter