Medieval music is still too chromatic for a whistle for the most part. Too many half holings required. Some pieces do work pretty well though. Even some Baroque-- The opening Air of the Goldberg Variations makes a smashing slow air if you toss in a few Celtic ornaments with only 2 or 3 half holes needed.
And
there
is this
pretty
GIRL!
Oh, was I reading between the lines?
I’m a cross-fippler, too, but I’ve never used my recorder to play medieval music. I use it to play Jewish music. (I also sing in Hebrew.)