Hey Rusty, I say this with great respect...You have RYV, but I am not sure you have fully read it or are practicing it daily. The book talks about whistle and how I obtained it. And if you were practicing the exercises, you might have reached that 5th octave already;) Go back and re-read it, practice faithfully for 6-8 weeks and I bet you find it:) If you're a member of V, I will post a video soon of how to reach whistle with the pocketVox:)

I'm not sure if I'm at Whistle yet, but the exercises are definitely helping (the Hoo falsetto has really helped a lot with the second break)! Does whistle generally start at C5, or is it more of the G5 bridge? I've been stuck at G5 for the last year and can hit it in falsetto at karaoke, but it takes a lot of warming up even then, and I can't do it with strong adduction. There is a lot of talk about "vocal flageolet", particularly in the CVT terminology- but it's not really clear if that is reinforced falsetto or something else, and it also does not mention what pitch in Scientific Notation that would start at. I have RYV 2, which did clarify some things though, so the path to the finish line is coming more and more into view, and I've managed not to accumulate any vocal damage along the way, so that's not too shabby. :)

Flageolet is whistle. Mine starts around D6. I doubt yours would be starting at Tenor C or even G5 above. This just means you still have room to expand.

What I find confusing about the definition of Flageolet is that the CVT book talks about using it below C5 too loudly, which it says creates a split in the voice.

At C5 or just before, I feel something change- the pharyngeal tone takes over- and this is what I was thinking was Flageolet, but is probably just the start of pure M2 (or the closest thing to it).