I made a Low A today (and started a chromatic G Fife, but that’s less interesting).
God decided to bless me with longish fingers, So I decided I’d go for it. It was a difficult stretch on the last hole, untill I discovered this other finger dangling off the end of my hand, which reaches rather comfortably.
The real trick is getting my lips right to sound the A. I can’t do it 100% of the time, but practice will make perfect, it always does.
I have a couple of bamboo flutes in low A and low G.
I can, with effort, get them to sound, but I’ve never worked at it hard enough to be able play anything. The stretches are brutal and I fear tendonitis.
However, they make a lovely hooty sound.
I think I’m with you on the Tendonitis fear thing…
after practicing on it for about an hour, I find that my rist is a little sore.
I Gig once a week on the guitar, and I don’t think the people I play with would think it was cute if I couldn’t play anymore because messing around with Baritone flutes…
though I might be able to do one that low if it was only pentatonics… 
Large pentatonic flutes with only four finger holes are obviously easier to play than flutes with six finger holes. You finger the pentatonic flutes with the index and ring fingers of both hands, and the middle fingers fall between the finger holes to support the flute with the thumbs.