It seemed appropriate for me to eat a little humble pie.
I have made some mistakes in my recent posts about the GPO5.01 update released on the 1st of April.
Mea culpa.

My sincere apologies to one and all, including MM, Gary and his employees and contractors.
After considerable extra hunting around the sfz files, I have discovered a lot more about what has been done in the upgrade. Several of the sfz files have been renamed with a 'b' suffix, but in many cases the older files are still present.
So I became confused. Closer attention to detail on my behalf was definitely required.
Excuse = I'm fairly new to this.
Response = then you shouldn't shoot your mouth off, you idiot!
As far as I can see, the 'stereo stage' controls
have been inserted into the sfz files for the
SAM brass instruments.
So if you are sending cc#103 on or off messages, or cc#36 depth messages, they will be responded to, it appears.
At least, the code is there now within the newly written files.
However, what fooled me (yea, I know, it doesn't take much!), is that the corresponding xml files, which govern the
appearance of the controls within the ARIA user interface are not present.
So, although ARIA will respond to the MIDI controllers (it appears), one is unable at this time to affect control from within the ARIA window. My altered GUI would achieve that. So I must set to and complete that.
I am still of the opinion that no changes were made to the samples, and various exchanges of PMs would appear to confirm that.
So ... If you would like to do the upgrade without re-downloading the whole four and a half gigabytes then,
providing that you have the original zip file OR the unzipped files within a separate library (NO, not the installed samples) I can provide you with the "WIN_Garritan_Personal_Orchestra_5.01.exe" file that does the upgrade for Windows.
The file is about 44 megabytes in size.
Sorry I don't have the file for Mac.
Running this file will do the ARIA upgrade and various other bits and pieces
PLUS insert the new xml and sfz files
BUT it will also reinstall all the samples from the original sample set, a long winded process. It will, at least, save you the download time of the 'complete' library.
The file needs to be unzipped and placed alongside (NOT within) the SamplesData folder/directory usually found within a folder named "Garritan_Personal_Orchestra_5" but NOT the one within the Program Files folder/directory.
It replaces the original GPO5 dot exe file.
If you're unclear please PM me.
If you want the file please PM me.
Sadly, if you don't have the original GPO5 SamplesData directory, then you'll have to download it all again. So sorry.
Again, my apologies to all if I misled you.
Regards,
John.
Please note:
E&OE.
You do the upgrade at your own risk.
I am NOT responsible for any upgrades that you may do as a result of this post.