I just installed and messed around with TouchDaw using a 10" samsung Tablet.  
It was easy to set up and it works well for basic functions, but not better than my MCU pro and C4.
 
 
I can access the first prochannel module (whichever I place first) which is encouraging, BUT
only the first 8 parameters
and only the 1st module
nothing from the fx bin (even if i put PC in "post" mode).
 
Am I missing something, or is this it?
I would use this product JUST for it's ability to control PC modules.
 
 
 
 
 

For at least some meaningful PC control (EQ and Compressor) you need my mod:
https://github.com/AZSlow3/Cakewalk-Control-Surface-SDK/tree/dyneq
From that you need the plug-in MackieControl.dll with correct bitness:
https://github.com/AZSlow3/Cakewalk-Control-Surface-SDK/tree/dyneq/Bin
and the mapping MackieControl.ini (put it into the same folder):
https://raw.githubusercontent.com/AZSlow3/Cakewalk-Control-Surface-SDK/dyneq/Surfaces/MackieControl/MackieControl.ini
 
I repeat, only PC EQ and standard PC Compressors will be controllable as in the documentation (independent from there position in PC). All other PC modules will be "invisible".
 
FX bin should work in "Plug-in" mode. EQs and Compressors in FX bin can also work in corresponding modes in case you define them in the .ini file manually.
 
ProChannel modules are control surface "unfriendly". VS-700 works with them throw ACT dynamic mapping (as you know unsupported in Mackie Control plug-in).

I will certainly give this a shot.
Will this increase the functionality of BOTH my MCU pro and the TouchDAW app?
Or is it just to help one or the other?
Thanks for all you efforts!

That is for all devices, your MCU pro will get the same functionality.

So, it's the weekend and I'm snowed in for the day.  But I must confess that I don't know what to do with the links you provided.
Is there an earlier thread with directions or a readme with step by step instructions?
 
I don't have any coding experience.  What's involved in implementing this mod?

Nevermind, Azslow, I registered at your site and it then became obvious.
Thanks for all your work!

Well... my site is not about the mod I have recommended to you. It is about completely different closed source but free to use plug-in, developed form scratch my me. I have MackieControl preset for my plug-in, which mimic most parts of original one. It can work with ProChannel. It works throw ACT instead of special way implemented in the original plug-in. But there are several weak points: this preset is not really tested, does not support C4 nor XT. Not that it is not possible, but that takes time and requires cooperation with someone who has real hardware (I do not).
 
I have pointed you to my modification of the original plug-in (open source). So you get everything you already have but with fixed EQ/Compressors. My announcement was there: http://forum.cakewalk.com/FindPost/3311275
 
To deploy, you need 2 files from posted links, MackieControl.dll and MackieControl.ini. The first should have the same number of bits as your Sonar (64 for 64bit Sonar, 32 for 32bit Sonar, even on 64bit Windows). Put them into the directory where you already have such files (using Windows search to find them, otherwise try open "C:\\Cakewalk\\Shared Surfaces"). Do not forget to backup old files!
 
Also if you do not have it, you need Microsoft runtime 2015. I forgot to mention that before.

I will follow these directions. Also, feel free to message me if you need anything tested- I have the mcu pro and the c4, but no extender. I also recently tried out the touch DAW app on a Samsung tablet.
Or email blixyz@gmail.com