A big part of installing plugins in the Notes 8.x / Expeditor client is getting the File/Application/Install menu item to show up for users. Bob Balfe has an interesting post on this very topic for the upcoming Notes 8.5 client.
Problems enabling the Application | Install menu in Notes 8.5 beta
lekkimworld.com 
Thanks! I was searching for this and found this post via Google.
Ironically, I was searching for it because of this post of yours. 🙂
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