It sounds like you know more about tuning than I do, jeff. But here is a March, 2014 tuning chart for my Suzuki M-32C for comparison:
Notice that the most extreme initial readings (with the exception of E4) are toward the ends of the keyboard. This is typical, for whatever reason, and is even more conspicuous with an older out-of-tune melodica. Well, the F3 end is nearest to the mouth (and the C6 furthest away). I tend to get different readings at F3 depending on whether I’m using the mouthpiece or not.
The factory tuning of my other current metal-tray Suzukis (A-34C and M-37C) has been comparable in quality — not too bad in comparison with other melodicas.
The M-32C is a great Melodion, one of my favorite melodicas, alongside the Yamaha P-32D. In my experience, it’s easier to get consistent readings on the Yamahas but not as easy to bend notes.
I think there would be a lot of interest here in your experimentation with a regulated air hose, jeff.