CF Text box change

Hello - I’d like to customize a custom field, specifically, the text box
(textarea), and make the width 40 cols instead of 15. I don’t know if RT
calculates this dynamically, since it can’t know how many custom fields I
added to the Ticket and what type they are. Is this okay to do and would it
be done by adding a callback or by other means?
L. Evensen