I started out making PVC flutes ala Doug Tipple almost a year ago.
His numbers and photos on his website really helped a lot.
Ive built a bunch of both six hole and eight hole.
About 20 so far. (its been slow going, but I made up for it reciently
)
Many of them non tunable as I was just messing with the tone holes.
I found Flutomat and TWcalc are really great to see how things are interelated (bore, chimney, length, hole size to placement)
I think I have got a begining handle on the basics for cylindrical bore… the VERY basics.
Like how to make and use a zero rake bit as to not impale yourself,
loved ones, pets and nextdoor neighbors when the drill bites hard
and turns your nascent flute into a javelin! 
Always wear eye protection and dust mask BTW!
When I started messing with embouchure cuts it dawned on me that
I was being really stupid. I had a few pipes that I didn’t care for
the mouth but liked the tone holes. (o.k… many I didn’t care for completely.
)
I measured off one and cut off its head!
Added a joint couple and made a few different head joints.
Experiments at a few pennies a pop.
I then my second “Why the heck didn’t I think of this before”
I made a few fipples with hardwood plugs and voila!
Instant low D.
I have a feeling there is another affliction similar to WHoA.
It is related Im sure.
I had to buy Doug’s “bells and whistles” D just to see what I was missing out on.
Well.. lets just say mine are different…
and I’m playing his constantly.

I gotta get me a lathe!
And more flutes…
And more whistles…
