I'm not fast, am just doing the 1/2 size one
The first year I did the mystery I was bored stiff the first two clues because I was expecting so much more to do.
So I started a second one. Error.....
One is plenty and 1/2 is just right for me this year. 75" square is a pretty generous quilt size. And we don't know what the border will look like yet, if it's yummy I could upsize just with that.