I'm planning to flyfish Big Twin near Winthrop this weekend. I'd appreciate any advice or recent reports.

I havent fished there the last two years, but the fishing was good. The northern end of the lake was good using black wooley buggers, And at night in the shallow coves with a black bunny leech.

I was there in June and the water is incredably low this year in both lakes. The great reed beds that used to line the coves to the right of the access are gone. All of the best coves are so low on water the fish don't use them any more during the day.
Suspect you will need to go deep in the center section with buggers and leeches,or maybe try chronomids at the deeper water in front of the coves if a hatch is showing.