Mesterton-Gibbons is a single, hyphenated last name, which begins with M
and has seventeen characters including the hyphen. If you find it long
then there are two logical ways to abbreviate it. If you consider a
hyphenated name to be primarily a long word, then the logical abbreviation
of Mesterton-Gibbons is Mesterton. If you consider a hyphenated name to be
primarily a compound word, however, then the logical abbreviation of
Mesterton-Gibbons is M-G (which I prefer).