Around the year 2002, I created a whistle called the "Bathroom Great Bass".  It was a Low-Low-C or Bass-C and had large diameter 3/4" to 1" toneholes that were covered using square pieces of PVC pipe that would cover the hole and follow its round contour.   It then had springs and pivot for each hole and then long square rods that came up to the hands in order to operate the keys.  It was straight and the bottom sat on the ground.   The rods were alway coming loose.

About a year later, I decided to rebuild it.  This time using have a trap fitting from PVC stock to flip the mouthpiece over  upside down.  This also created a way to deal with moisture by have a cap that is removeable.   Then I made keys from flat brass and bent them to follow the contour of pipe.

During that time of development I created a yahoogroup group on making basswhistles.
Drawings for the fipple and keys were published there but the plans did not cover the entire instrument.

The keys had a central rod running the lenghth of all six allow them  to be removeable.
A large rod with coiled springs held the keys open.
In 2011, the keys were changed to use leaf springs like that used on Clarinets.  About 0.6 inches long approximately.  

The latest design was much easier for anyone to hold and play.  The fingering does not require as much pressure to operate.

Basswhistles have been made available from Bass-C to Low-A but only Bass-C and Bass-D have been sold.    To date, only a handful of Basswhistles have been made.

Another hybrid of the Basswhistle is the Sub-NAF, which is fingered like a Native American Flute and it has a lower length to bore ratio which makes it play one octave and few extra notes but it has a more deeper and haunting sound than the basswhistle.

Some basswhistles were fitted with a piezo pickup with a 1/4" jack and can be plug into an amp.  This is still available upon request.

I plan to relase a book on making the basswhistle.  It will be an extensive coverage of the design and it will likely be published through createspace.