Guessing large is the worse case in this situation, so by counting them at seven letters it's managing expectations. It also depends on writing style quite a bit, I'd imagine. Grabbing around half of DW2-6 just now and dropping it into LibreOffice to use the word counter, I get 12,649 words with 59,097 characters excluding spaces, which does indeed look pretty close to five letters on average. 4.67, to be precise, so yeah. Actual results should be higher by up to around a third.
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‎noli esse culus
‎noli esse culus