In "Two New Transdeletion Pyramids" in the May 1988 Word Ways, the editor gives two 17-letter transdeletion pyramids found by Kyle Corbin, the first of which consists of words from either Webster's New International Dictionary of the English Language. I believe that a word found in Webster's Third is better than one found in Webster's Second but not the Third, because (whatever the faults of the Third or the merits of the Second), the Third superseded the Second.Accordingly, I pass on three 17-letter transdeletion pyramids consisting entirely of words in the Third or inflections implied by the Third, assuming that section 4.1 of the explanatory notes is deemed to allow indiscriminate pluralising.
"Three New Transdeletion Pyramids,"
Word Ways: Vol. 34
, Article 17.
Available at: http://digitalcommons.butler.edu/wordways/vol34/iss3/17