Hello all,
I’m a part time whistle builder and I’m looking for some information for my next big project. I am trying to build a low (below low D) G whistle without keys. Instead of trying to calculate the hole positions and trying to make the holes within reach myself, I thought it would be easier to get the dimensions from a whistle that already exists. If anyone has an Overton low G or similar whistle I would appreciate you providing me with the inner diameter, hole positions and hole diameters.
I’ll be sure to post pictures when I’m done.
Thanks in advance!
Without keys? Wow, the market might only be for NBA players!
Welcome to the exciting world of whistling and whistle making. 
The easier way to find the dimensions you request is an ancient oriental technique used in the USA often. Buy one and copy it. 
Or just use the per cent method which is available in the search feature of this forum in the upper right hand corner of your screen. If your patient enough I will post the measurements of my bass A below D and then you might determine first if you can reach/play a bass G.
If you’re using CPVC and have good ventilation, you could use a heat gun to soften the material and bend it, kind of the like the old Serpent horns. Might make things easier to reach.