The pivot indicator length can set from the FontMetrics.bottom - more info can be found here http://evendanan.net/2011/12/Font-Metrics-in-Java-OR-How-the-hell-Should-I-Position-This-Font/

While the top and bottom padding can be determined by multiply the pivot indicator length by 2 which should make the indicator line never overlapping the pivot letter

The attributes padding, paddingTop, and paddingBottom will be additional padding for the calculated padding in the above statement.