Mike, Lots of good info from the folks on the PMF. I found out that not all things you think are straight, are straight.
Space here for the necessary gags and comments before continuing.
As I chased the lines on the stem/shank I got curious about the piece of cast off I was using as a straight edge so I checked it and found that it had a few very small bumps especially on the tips. So I rummaged around and found something better that I checked and IS straight and flat until I can purchase the machined billet steel blocks suggested by PMF members.
I got a bit too aggressive at the bowl/shank interface and it curves in where it shouldn't. Next one will be better.
I got some really great feedback on cutting the slot that will also be incorporated on next attempts and I did get rid of the hour-glass restriction that was in the airway.
I like the ergonomics of this iteration much better. At least to me, it feels better in the hand than the former with the shank belly. It has beautiful draw!
I am not sure what 'blocks' you are looking for, but snoop out machinists' parallels and 123 blocks. Both can be had cheaply and are for all practical purposes flat and straight.
For example, these 123 blocks are about 8 bucks on ebay and are ground within .0003", which should be close enough for wood working. Three tenths is pretty close.
And anothre example, a 20 piece set of parallels is 35 bucks from Harbor Freight. Smaller sets can be had used on ebay too.