Darryl Francis presented a neat idea in "Balanced Word Pairs" in the November 2004 Word Ways. I do, however, prefer a name like "complementary word pairs" because the corresponding letters in each word are the 27s-complement of each other. i do not see how the word "balanced" applies, as it does with balanced words. Darryl found just one example of length 6; I found another 150 of this length (mostly by using place names). I also found nine of length 7 (ignoring words consisting of strings of up to 23 As). The following selection of length 6 includes cases where both words are to be found in a dictionary or similar reference, or where one word at least is familiar.
"More Balanced Word Pairs,"
Word Ways: Vol. 38
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol38/iss1/9