This article concerns words of high and low density, ie a large sum with respect to the number of letters. A recent effort by Susan Thorpe (Lighter and Heavier, Word Ways, August 2003), also details previous work. She (deliberately, one supposes) omitted words, variously sanctioned by the OED and the Palindromicon, of length 5 or more, consisting solely of a repeated letter: I follow her in not using about 24 examples of repeated letters A, X, and Z.
"Denser Yet, And Yet Less Dense,"
Word Ways: Vol. 37
, Article 15.
Available at: http://digitalcommons.butler.edu/wordways/vol37/iss3/15