Read-only lookup fields are displayed so that the field width is determined based on the length of the name.
For lengths N:
<= 10 characters, the width is set to N em
> 10 characters, the width is set to N ex
> 50 characters, the width is set to 50 ex
Tim Gething has suggested an alternative here: http://www.openvpms.org/comment/reply/4269/6945#comment-6945
less than 7 characters: Nem
7-24 characters: N+3+round(N/5) ex
25+ characters: N+round(N/8) ex
Another possibility is to develop a new label component that has the same L&F that displays the characters up to a maximum length.
Currently the fields are displayed using read-only input fields.