In the November 1982 issue of Word Ways, I exhibited a palindromic alphabetic insertion based on AA, a type of rought, scoriaceous lava. A complete list of 26 words was found, starting with AAA, ABA, ACA ... through the AZA.
"Another Palindromic Insertion,"
Word Ways: Vol. 25
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol25/iss3/9