I only got around to starting this puzzle on Wed 29th Nov (which was obviously too late for the submission date of 30th Nov), but decided to give it a go anyway for the sheer enjoyment of trying to solve it. At that point, I was unaware that this thread existed, and was pleased (having gone down several blind alleys in the process), to crack the first (numerical) part of the puzzle plus the "3-part hint" referred to at the beginning of the second part, without any 3rd party assistance.
So, armed with 20 letters in the first grid and 19 letters in the second grid, I then applied myself to the remainder of the second part of the puzzle, and that's when I started to feel uneasy. I think it was Ximenes who coined the "rule" that compilers must follow :- " You do not have to mean what you say, but you must say what you mean ".
Prior to making the comments below, I wish to say I have always had the highest respect (over several decades) for the scrupulously accurate wording used by Listener compilers in their preambles to the puzzles I have tackled, because they always adhered to Ximenes' "rule".
My uneasiness is centred on the third sentence in the second part of the preamble :- " Another part of the hint says what the solver must do to the positions of
the (my italics) letters in the first grid to arrive at the second grid, thus enabling the grids' completion ".
Because of the the word "VarY" in the second part of the three-part hint, it seems reasonable to transpose this sentence into " Another part of the hint says that the solver must vary the positions of
the[i/i] (my italics) letters in the first grid to arrive at the second grid, thus enabling the grids' completion ".
I believe the phrase "the[i/] (my italics) letters in the first grid" has to unequivocally mean ALL of the letters in the first grid, and is not (following Ximenes' rule) a valid way to define "some of the letters in the first grid" or "certain letters in the first grid" - which is what the compiler is actually referring to, i.e. what he actually means.
I only realised what the compiler actually means by coming across this thread and reading crosswhit99's very helpful comment (No 18):- "Add the four letters that appear in the first grid but not the second to the second, and the three from the second not in the first to the first".
Following this advice is essential to cracking the next part of the puzzle, but it requires intuitive/proleptic analysis that is not justified from the preamble
It also involves a second piece of proleptic analysis not justified by the preamble, namely the extra requirement to add letters from the second grid to the first. This point was made strongly by dryden in his postings (Nos 53, 54 and 56) and, in my opinion, he is totally justified to complain that the preamble tells the solver some of the steps he/she has to follow, but not All of the steps to be followed.
The final issue, as referred to (only) by meursault in Post No 55 is :- "Then 1 letter is added twice to each grid in the 2 remaining positions on each".
Again, proleptic thought is required. The preamble doesn't cover this
It is likely, given the last posting on this thread was 10 days ago, that no-one will even read this comment from me but, if anybody does, I would be grateful for feedback re my principal complaint relating to the unnecessary use of "the" as explained above, when it could so easily have been avoided.