A Perfect Storm Replacement Stem (pic heavy)

I haven't posted any shop work in a while because it's usually a case of "same thing, different day". Seen one, you've seen 'em all.
This one was rather the opposite. At first glance it looks simple enough, but it was anything but. One of the five or so toughest projects I've come across.
Here's the technical story:
There are several stummel shape details that make creating a replacement stem for it (in this case a second, switchable stem) especially difficult.
One is when the shank is square or square-ish; another is when there are small radii involved; another is a mortise that is not centered; and still another is when the shank is neither parallel-sided nor tapered, but flared.
On the stem side of the equation the categorical killers are length---the longer a stem is, the harder it is to keep things straight---and if it is faceted. (Every variation of round, oval, and bladed are a walk in the park compared to cutting gemstone-like facets with straight edges. The reason is because "there is only one straight line" in geometry, and the slightest deviation from it can be seen by a 16 year old pug dog from thirty feet away.)
So, imagine my joy when someone wanted a replacement stem that required dealing with ALL those things. :lol: An extra-long faceted stem for a stummel that WASN'T STRAIGHT ANYWHERE. Compensating for the offset and dimensional inequalities to make everything LOOK straight in the end was the name of the game
Anyway, that's the background, here are the pics. The first three show the shape of the shank, the second shows how far off center things were (the stem was inserted upside down to illustrate), and the third shows the slight trumpeting of the shank (the side view isn't shown but it also flared). The next three show the sausage being made, and the last three show the final result.
-





-





-

Cool that yer diggin' it. 8)
Also, thanks for the kind words. :D
And a P.S. -- The problems described aren't nearly the result of something Bjorn did or didn't do as much as the geometry inherent to the shape / design. The pipe wasn't INTENDED to have a 4-inch taper stem. Few (if any) pipe makers consider whether or not what he's making will present difficulties for a future repairman, in any event. Except for a few fundamental things, it isn't their job. No foul there, at all.
Having the full array of things that make a stem replacement difficult converge in one specimen was just luck, which is why I took the pics & etc. Like a reverse lottery win, or something. Noteworthy because of its rarity. :lol:

Damn, guys. Thanks again for the props. :D
Repair work is such a limited interest thing that knowing people care about it (besides the actual owners of the pipes, of course) is exciting for me.
Someone called me tonight to ask if there were any "tricks" involved in keeping things straight on long, geometric stems like this BingDog, so I figured there might be others who are wondering who didn't ask.
So here ya go: At all times until the very end of shaping when it must be erased, keep a guide line in place. I start with a 1/8" strip of masking tape that's exactly centered over the slot, and lay it down tight and straight to the center of the "peaks" on the sides of the shank. Then, as the stem reduces to the point that tape can't be maintained, use the roughened, different color surface of the stem itself as a stripe. Think sharpening a knife edge but never quite getting there, leaving the edge slightly square in cross section. If you look closely at the second pic, what almost looks like a strip of tape is actually just vulcanite that's a lighter color because it has a rougher surface that holds dust.
The rest is just understanding what "dwell time" is when sanding and filing, and checking often both by sighting down all straight lines and using a machined straightedge to check for light gaps.
.