I just got my 8-key Firth Son & Co flute back from repairs by Jeff Denning & Jay Hamm (*). Excellent work from both craftsman made this flute look almost new, and it plays beautifully. This is probably the largest holed American flute I've ever seen, from the tail end of the Firth, Pond, Hall family tree - 1863 or so, smack in the middle of the American Civil War.
These flutes play at A440 with good intonation. "Large" hole size means it is along the lines of a medium-sized R&R flute. With a metal embouchure jacket the tone is clear and round rather than reedy with resonant over-tones. The volume is as strong as my excellent R&R. Perhaps the low D is a little louder, but that could have more to do with the quality of the tone rather than volume.
But the really nice thing about this flute is the ergonomics of the C-nat and the short F-nat keys.
The C-nat key lies just under my slightly curved right index finger. Slightly curved but almost piper's flat. That means that to actuate the C-nat, I merely have to straighten my right index finger causing the second pad to lower. This is super fast, compared with other flutes where I need to move the right index finger up the flute a little.
Secondly, Even though I almost exclusively use the long-F, the short-F key on the FPH family has a little indentation in the flute so the key sits lower. Also the key is typically twisted so the third right finger can easily slide off the key to cover the D-hole. If my finger was fatter, maybe I could even roll it from D to F-nat. On most flutes you have to pick your finger up to depress the key.
I do prefer the Eb key on my R&R which happens to have a pewter strike. As a result the spring tension is very light.
(*) As to why I sent it to two different repair guys. The silver embouchure sleeve had slipped about a mm causing the tone to be fuzzy. Jeff was suitably nervous about applying too much force. I sent it to Jay for a new embouchure cut or else a new head. He said, "what the heck, it's silver, I'll just crank on it", and voilá, it slipped into place.