I first present a list of just over a hundred sumgrams (words with equal numerical value) of the longest words I was able to conquer. Note that one pair of reasonably common words could be construed as opposites: EXTRAORDINARINESS and STRAIGHTFORWARDNESS. Note also that all pairs of words with endings -IST and -ISMS are sumgrams, as the values of M and S sum to the value of T. I have included the longest such specimens in my list.
"Sumwords: Record Scores and Anagrams,"
Word Ways: Vol. 23
, Article 14.
Available at: https://digitalcommons.butler.edu/wordways/vol23/iss1/14