So far only I've managed to discover that regular shapekeys (those without 'left_/right_' sliders) are working straight from BleST. On 'stereo' ones, as I said earlier in post #3, there's list of cotrollers but none of them is changing mesh at all.

Here's dropbox link same mesh with regular and stereo shapekeys set via custom flex controllers (also included)
https://www.dropbox.com/sh/578elda1lm43sl5/AAATHZwU8rTVS6J5Q99-GPJJa?dl=0

in short,
- regular shapekeys ( "stereo" "bool" "0" ) work
- stereo shapekeys ( "stereo" "bool" "1" ) doesn't change mesh at all in S2 Model Editor

to get to Morph sliders in Model Editor, select 'Tools' Menu, 'Morph Explorer', and then 'Enable Manual Slider Control'

(sorry for engrish)

EDIT: oh, and i'm not sure if material used by model need to be set to 'Hero' shader with "Morph supported" option check for morphs to work at all :/
http://i.imgur.com/WqyYMLZ.png

did you figured out how to get stereo shapekeys/flexes/morphs to work yet?
I doubt that's bug on BleST side, but just wanted to ask.

okay, small progress.
Seems like setting "stereo" to "0" when using custom flex(morph) controller, makes them work correctly.

The only problem I had so far with getting models to Source 2 was shapekeys (or 'morphs' as they now calling it).

It's like... there's list of all shapekeys (even those without controller/s), all defined controllers are there, but those seems to do nothing to the model.
I wonder, if it's just undocumented (yet) things to add in existing DMXs, or different setup for those in S2. :/

Well, just to think the easiest solution was the hardest to find :V

Default setting for Trianguate modifier's 'quad method' is 'Shortest Diagonal' that works exactly as you described few posts ago. 'Beauty' method gives nearly same result.
On either 'Fixed' or 'Fixed alternative' method those bugs went away.
Tested on both 2.3.1 and 2.3.2b1 you have posted.

I made some googling and find out that, according to Blender's API Documentation[www.blender.org] 'quads_convert_to_tris' operator (which is essentially 'Trianguate modifier' and is used when no active 'Trianguate modifier' is found on model) defaults to 'Beauty' quad method and gives errors on model's .vta.

tl;dr: Looks like Trianguate modifier on right settings fixed problem for good

As you already suggested, I've switched to .dmx, so let's just hope that bug will not show up on .dmx too :)
Thanks for help.

tbh no, but I'll try it tommorow.

oh, the rotation... well, good to know for future :)

umm...
shouldn't this line:
look like this?:

Okay, time for DMX then :V
I got an idea for workaround, but 'till I'll learn Blender's Python stuff, let's just leave it as is

For now, I'm marking vta as "unfixable" (you can change it later to whatever you want I guess).
But thanks for all help so far :D

ps. I'll miss ya .VTA

well, looks like normals are fixed, but now some vertices' position got a bit scrambled
video: http://www.youtube.com/watch?v=_gzddkesozY
picture with activated flex: http://i.imgur.com/V4Dxelj.png

and yes, after little over 2 years of stable .SMD usage, it's time to switch to unknown (at least to me) waters of .DMX format ...
... after that one vta bug will be squashed, ofc

EDIT: I've updated thread's topic to mark what's fixed