I also use underscores but use 8. It gives a little more room on a report to addin the correct name.

Mary ________
________ Jones
________ ________

There is *minor* bug in using blank, underscores or ?, etc. in the surname. A middle initial of I gets interpreted as a suffix (1st) Jane I ______ becomes Jane _____ I. This happens unless the first character of the surname is alpha, or you add more characters to the middle name, I() "I", I?, Irene, etc.