Mike,  I have scaled and built several sets of Vienna flute clock pipes
for different clock collectors and restorers.  The ranks I have built
consisted of 8 pipes or less (one of which was mitered).  Among the
collectors I built them for was Frank Snider of New Jersey.

I concur that these pipes were designed to play very softly ( for use
indoors).  But more importantly, I think, is that they were used for
their efficient use of the limited air (1/2" or less) generated within
a clock.

You stated "The builder/voicer need not adjust the flue to direct the wind
sheet at the upper lip."

The pipe I copied and scaled, had a rounded slit to produce the wind
stream.  I believe this slit controlled the shape of the wind stream,
while a wedge under the front block was used in conjunction with the
block location to direct the air stream over the (inside) tapered round
hole for voicing.  The locations of all these pipe parts were very
important in the voicing process.

If I can be of service in you building your pipes or building pipes
please contact me for further information.

Gary G. Stevenson
Musical Box Society Member from St. Louis, Mo.