Ok, well it seems that there is an inconsistency between the wrapper formats then.
The problem that we were originally trying to solve was that in pre-multibus some plugins (GLow Windows VST was one that was reported to us and we were testing with) opened in stereo, now, post-multibus it opens in mono. This was detailed here: Stereo VST appearing as Mono
Therefore, the default behaviour by JUCE has changed.
At the end of the thread you recommend to open to change the channel layout to stereo if it supports that. We did something similar to this but thought that the old behaviour would be opening the maximum number of channels so decided to iterate all the possible channels and try and open the maximum.
The difficulty here is that I’ve really know way of know what the old default behaviour was for all the various platforms and formats and then trying to match it up in our app by changing the channel layouts. We can’t just blindly set the layouts to stereo, what if someone wants to use a 16-out plugin and we set it to stereo, they will have lost all their available channels.
I guess the question really is what was it about pre-multibus that opened GLow in stereo rather than mono if mono is the default (as would explain the mono opening of post-multibus).
If I can figure that out, perhaps I don’t have to try and open the maximum number of channels for all new plugins and just leave it at the default (which would be my preferred choice).