Here's my question about the above design... Do any of you see any problems in how I have the air passage place between the chamber bottom and the shank?
With your current design, it looks like renegade tobacco chunks might be hard to clear out if they fall into the vertical part of the draft hole. A pipe cleaner won't be able to reach that spot after you have tobacco in the bowl.
I had a pipe with air passages like that once... serious PITA. I kept two drill bits with it which I rotated with my fingers to clean it out... got really tired of that routine and eventually ditched the pipe.
If you can remove the angle and let it transition smoothly, which I can hardly imagine being easily doable, it might be fine.
Otherwise, that 90 degree angle looks like a pain to deal with, and the airway seems to be tight as well, in that area.
You'll have huge turbulence there and it will gurgle like crazy, and after about 20 smokes, you'll plug it up and not be able to clean it......Drill it deeper so the draft meets the bottom correctly and you'll be happy.......
A draft hole going straight down through the bottom of the bowl has to have an open sump area, like a classic calabash design or a Falcon-type design. Otherwise, the 90-degree bend will become the moisture-collection point as well as the choke point for loose tobacco bits.