For five-letter words, over 60 per cent of words are heterograms, fewer than 2 per cent are isolanos, over a quarter onalosis, and each word has almost 13 neighbours on average--over two per letter. On the other hand, there are not many more than half the number of words to choose from compared to six-letter words. Also it is not possible to have sequential replacement between reversals: from ABCDE to EDCBA would proceed via EBCDE, EDCDE, then EDCDE again, and an implicit conditions of all our ladders is that no word should be repeated, so we will not find reversals between word with odd number of letters.
"Five-Letter Connoisseur's Ladders,"
Word Ways: Vol. 34
, Article 13.
Available at: http://digitalcommons.butler.edu/wordways/vol34/iss2/13