Edit: I should have mentioned I'm on an iMac running MacOs Mojave 10.14.3 (18D109) with 8GB. The older MacOs versions seem to be causing issues and I thought I should add this update. I also did a fresh from scratch Mojave install with all partitions wiped and installing from the "Command + Option + R" option during power up, which installs directly from the web without needing physical media.
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I just completed installing and using the MAX 4 plugin in Studio One 4. The indexing took a while as expected. At first none of the ST3 stuff was available, but I simply added the ST3 path to the plugin and it re-indexed and now all instruments are available and appear to be working without any issues. I loaded a couple of the ST4 Pianos and they loaded and played without any issues. Yes, they took up some memory, but my Mac OS activity monitor showed that memory used by Studio One 4 with the ST4 Piano loaded was a little over 3GB. I have 8GB of memory of my iMac.
The issue of 3 instruments showing for each instrument is still happening in version 4.0.1, but hopefully that will be fixed in a future update. I don't see it as a critical issue.
Next, I'm going to install Syntronik Deluxe, which I've been waiting to install after ST4 MAX was released. Overall, except for the issues I had with the .zip files and the "strings" .dmg files, which I was able to fix (see my last post), I feel that this has been a very positive, but lengthy upgrade and I'm glad it's done!
Thanks- Dave