I'm setting the Coordinate System of a data frame that spans the equator. In the past, working in non-equatorial regions but where the data frame horizontally spans two UTM zones, I have selected the UTM zone that most covers the data frame. However, I don't believe my method has been correct.
I have a data frame that mostly displays the N hemisphere, but has a strip at the bottom which is in the S hemisphere. Following the above method, I set the coordinate system to WGS 1984 UTM Zone xxN. However, this has resulted in no latitudinal MGRS labels, except "0" for the equator and "1000mN" for the latitudinal line 1,000m SOUTH of the equator (which incidentally is recessed in towards the data frames' neat-line).