I can't answer directly but I did this loop this past September and took the other route into McGarvey, going south from Big Porc through the Double Devil's Staircase. You can read my trip report here:
https://algonquinbeyond.com/trip-report ... algonquin/I did make a thread on Algonquin Adventures in October 2020 asking the same question as you and got a few responses:
https://algonquinadventures.boardhost.c ... hp?id=3039
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