Hi CL,
By 'superfluous' do you mean empty? If so, no, I have only one empty cell, the cell between 7 and 11 is filled by a letter from the entry to 27-4.
Yes, for 17-30, it's the first word that's acted on, pius unusual 5-letter word for 'string'.
Change 2nd letter of 2nd word and 1st of 3rd word (not Inc. The 5-letter word that goes in the empty cell)
I really enjoyed this, good fun and a real challenge!